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United States Patent |
5,231,143
|
Abraham
|
*
July 27, 1993
|
High-temperature oil-resistant elastomers
Abstract
High-temperature oil-resistant elastomers are prepared from butadiene
alkenylpyridine copolymers, butadiene-acrylate copolymers, and copolymers
of butadiene with 1,3-dienes containing fluorine. The unsaturated olefinic
backbone and pendant unsaturation derived from the hydrocarbon diene of
each of the copolymers is hydrogenated to a high degree by a catalyst
which improves the heat resistance of the copolymer without hydrogenation
of the polar groups thereof which would lower the oil-resistance of the
copolymer. A complexing agent for the hydrogenation catalyst prevents
poisoning of the catalyst by the polar groups of the copolymers thereby
enabling the catalyst to complex with unsaturated sites along the olefinic
copolymer backbone to achieve high levels of hydrogenation thereof.
Inventors:
|
Abraham; Tonson (Elyria, OH)
|
Assignee:
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The B. F. Goodrich Company (Akron, OH)
|
[*] Notice: |
The portion of the term of this patent subsequent to February 19, 2008
has been disclaimed. |
Appl. No.:
|
889661 |
Filed:
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May 27, 1992 |
Current U.S. Class: |
525/326.2; 525/338; 525/339 |
Intern'l Class: |
C08F 008/04 |
Field of Search: |
525/326.2
|
References Cited
U.S. Patent Documents
2836583 | May., 1958 | Crawford.
| |
2951063 | Aug., 1960 | Bolstad et al.
| |
2951064 | Aug., 1960 | Lo.
| |
2951065 | Aug., 1960 | Lo.
| |
2975164 | Mar., 1961 | Crawford et al.
| |
2979489 | Apr., 1961 | Le.
| |
3218303 | Nov., 1965 | Anderson et al.
| |
3308175 | Mar., 1967 | Barr.
| |
3379773 | Apr., 1968 | Barr.
| |
3398128 | Aug., 1968 | Bolstad et al.
| |
3416899 | Dec., 1968 | Schiff.
| |
3531450 | Sep., 1970 | Yoshimoto et al.
| |
3562341 | Feb., 1971 | Tarrant et al.
| |
3607850 | Sep., 1971 | Smith.
| |
3625927 | Dec., 1971 | Yoshimoto et al.
| |
3673281 | Jun., 1972 | Bronstert et al.
| |
3766300 | Oct., 1973 | De La Mare.
| |
3988504 | Oct., 1976 | Halasa.
| |
4041229 | Aug., 1977 | Pattison.
| |
4098991 | Apr., 1978 | Kang.
| |
Foreign Patent Documents |
1384143 | Jun., 1972 | GB.
| |
Other References
Chemical Abstracts vol. 68, 1968, pp. 7696-79692n.
"Oil Resistant Rubbers from 2-Methyl Vinyl Pyridine", James E. Pritchard &
Milton H. Opheim, Industrial an Engineering Chemistry, 1954, vol. 46, pp.
2242-2245.
"Butadiene-2-Methyl-5-Vinylpyridine Rubbers for General Purpose Use", H. E.
Railsbach 7 C. C. Baird, Industrial Engineering Chemistry, 1957, vol. 49,
pp. 1043-1050.
"Pyridinium High Polymers--A New Class of Oil-Resistant Synthetic Rubbers",
W. B. Reynold, J. E. Pritchard, M. H. Opheim, & G. Kraus, Proceedings of
the 3rd Rubber Technology Conference, 1956, pp. 226-240.
"Technical Report 68-56-CM Polymerization Studies Leading to High Strength
Chemical-Resistant Elastomers Serviceable at Temperature Extremes", D. I.
Relyea, H. P. Smith, A. N. Johnson, Feb. 1968, p. 8.
"Principles of Elastomer Synthesis", H. F. Mark, Journal of Applied Polymer
Science: Applied Polymer Symposium 39, 1984, pp. 1-19.
|
Primary Examiner: Lipman; Bernard
Attorney, Agent or Firm: Hudak & Shunk
Parent Case Text
CROSS-REFERENCE
This is a division of U.S. application Ser. No. 07/610,773, filed on Nov.
14, 1990, of Tonson Abraham, for "High-Temperature, Oil-Resistant
Elastomers," which is a continuation-in-part of the following pending
prior applications: Ser. No. 07/450,945 filed Dec. 14, 1989, now U.S. Pat.
No. 4,999,405 for "Compositions of and a Method for Preparing
High-Temperature Oil-Resistant Elastomers from Hydrogenated Butadiene
Alkenylpyridine Copolymers"; Ser. No. 07/450,947 filed Dec. 14, 1989 now
U.S. Pat. No. 4,994,528 for "Compositions of and a Method for Preparing
High-Temperature Oil-Resistant Elastomers from Hydrogenated
Butadiene-Acrylate Copolymers"; and Ser. No. 07/450,950 filed Dec. 14,
1989, now U.S. Pat. No. 4,994,527 for "High Temperature, Oil-Resistant
Elastomers from Hydrogenated Copolymers of 1,3-Dienes Containing Fluorine.
"
Claims
What is claimed is:
1. A heat and oil-resistant hydrogenated elastomer composition, comprising:
a copolymer including first and second monomeric classes, wherein said
first monomeric class is a polar fluorodiene having the general formula
##STR22##
wherein a is independently hydrogen or fluorine, R.sub.15 is hydrogen or a
fluoro alkyl group containing from about 1 to about 4 carbon atoms and at
least 3 fluoro atoms, with the proviso that both R.sub.15 groups are not
hydrogen, and R.sub.16 and R.sub.17 are independently fluorine, hydrogen,
or a fluoro alkyl group containing from about 1 to about 4 carbon atoms
and at least 3 fluorine atoms, and wherein said second monomeric class is
(a) a conjugated diene, a branched conjugated diene, or a mixture thereof
containing from about 4 to about 8 carbon atoms, or (b) a monomer of the
general formula CH.sub.2 .dbd.CR.sub.18 X wherein R.sub.18 is hydrogen or
an alkyl group containing from about 1 to about 4 carbon atoms and X is
2-pyridyl, 4-pyridyl,--COOR.sub.19, --CONR.sub.20 R.sub.21 or
--COOR.sub.22 OR.sub.19 wherein R.sub.19 is an alkyl group containing from
about 1 to about 4 carbon atoms, --CH.sub.2 CF.sub.3 or --CH.sub.2
CF.sub.2 CF.sub.2 H, R.sub.20 and R.sub.21 are alkyl groups independently
containing from about 1 to about 4 carbon atoms and R.sub.22 is an
alkylene group containing from about 1 to about 4 carbon atoms, or
mixtures of (a) and (b) wherein the mole ratio of (a):(b) is from about
1:7 to about 7:1, wherein the mole ratio of said first monomer to said
second monomer is from about 2:3 to about 4:3 wherein the weight average
molecular weight of said copolymer is from about 20,000 to about
1,000,000, and wherein the degree of hydrogenation of said copolymer is
greater than about 80 percent.
2. The composition of claim 1, wherein said conjugated diene is butadiene
or isoprene; wherein R.sub.18 is hydrogen or an alkyl group containing 1
to 2 carbon atoms, R.sub.19 is an alkyl group containing 1 to 2 carbon
atoms, R.sub.20 and R.sub.21 are alkyl groups independently containing 1
to 2 carbon atoms, and R.sub.22 is an alkylene group containing 1 to 2
carbons atoms; wherein the mole ratio of (a):(b) is from about 1:5 to
about 5:1; wherein the weight average molecular weight of said copolymer
is from about 200,000 to about 750,000; and wherein the degree of
hydrogenation of said copolymer is greater than about 85 percent.
3. The composition of claim 2, wherein R.sub.18 is hydrogen or a methyl
group, R.sub.19 is a methyl group, and R.sub.20 and R.sub.21 are a methyl
group forming a butadiene/1,1,2-trifluorobutadiene copolymer; wherein the
weight percent of the trifluorobutadiene monomer is about 67 percent based
on the total weight of said copolymer; wherein the mole ratio of (a):(b)
is from about 3:1 to about 4:1, wherein the mole ratio of said first
monomer: said second monomer is 1:1; wherein the weight average molecular
weight of said copolymer is from about 400,000 to about 500,000; and
wherein the degree of hydrogenation of said copolymer is greater than
about 95 percent.
Description
FIELD OF THE INVENTION
The present invention relates to high-temperature oil-resistant elastomers
prepared from butadiene alkenylpyridine copolymers, butadiene acrylate
copolymers, and copolymers of butadiene with 1,3-dienes containing
fluorine. More particularly, the invention relates to such
high-temperature oil-resistant elastomers prepared from the
above-mentioned copolymers, wherein the unsaturated olefinic backbone of
each of the copolymers as well as the pendant unsaturation derived from
the hydrocarbon diene, is hydrogenated to a high degree, which improves
the heat resistance of the copolymer without hydrogenation of the polar
groups thereof which would lower the oil-resistance of the copolymer.
BACKGROUND
Nitrile-butadiene rubber (NBR) is an oil-resistant elastomer used in
automotive applications, but has poor high temperature properties. The
recommended continuous use temperature is between 100.degree.-125.degree.
C. Commercially available hydrogenated NBR (HNBR) addresses the need for a
higher use temperature, oil-resistant elastomer having a continuous use
temperature up to about 150.degree. C.
Removal of the backbone unsaturation in NBR by hydrogenation increases the
heat resistance of the polymer while maintaining its low temperature and
oil-resistant properties. HNBR is mainly a random copolymer of ethylene
and acrylonitrile. HNBR compositions that contain up to 40 weight percent
bound acrylonitrile and 60 weight percent hydrocarbon segments have high
oil resistance and good low temperature properties. Higher acrylonitrile
content in the copolymer would further increase oil resistance, but would
be detrimental to low temperature properties.
Thus, although NBR can be successfully hydrogenated to form HNBR having
desirable thermooxidative stability or high heat-resistance, as well as
high oil-resistant properties, NBR must be hydrogenated utilizing a
homogeneous rhodium catalyst which is very expensive, thus making the
hydrogenated copolymer product economically limiting. The economical and
efficient process of the present invention cannot be utilized to
hydrogenate NBR since the pendant nitrile groups of the copolymer would
hydrogenate, thus lowering oil-resistance and also causing cross-linking
of the polymer chains making the copolymer product unsuitable for
elastomer applications. Therefore, butadiene-alkenylpyridine copolymers,
butadiene-acrylate copolymers, and copolymers of butadienes with
1,3-dienes containing fluorine are hydrogenated using the process of the
present invention to produce a high-temperature and oil-resistant
elastomer, wherein the unsaturated olefinic backbone of each of the
copolymers as well as the pendant unsaturation derived from the
hydrocarbon diene, is hydrogenated to a high degree which results in the
improved heat-resistance of the copolymer, without hydrogenation of the
polar groups thereof thereby maintaining the oil-resistance of the
copolymer. Again, these hydrogenated copolymers of the present invention
are produced in an economical manner, making them more desirable than the
expensive HNBR copolymers.
U.S. Pat. No. 3,416,899 (Schiff, Dec. 17, 1968) relates to improved gel
compositions useful as incendiary fuels, as solid fuels for heating, as a
fracturing liquid for subterranean formations, and the like. In another
aspect, this reference relates to the preparation of hydrocarbon gel
compositions by hydrogenating a hydrocarbon solution of an unsaturated
rubbery polymer in the presence of a catalyst comprising a reducing metal
compound and a salt of a Group VIII metal.
U.S. Pat. No. 3,673,281 (Bronstert et al., Jun. 27, 1972) relates to a
process for the hydrogenation of polymers containing double bonds in
solution and in the presence of a catalyst complex comprising:
A. a compound of iron, cobalt or nickel,
B. an organo-aluminum compound, and
C. hexaalkylphosphhoric acid triamide as activator.
Polymers of diene hydrocarbons contain double bonds in the backbone. These
double bonds may be hydrogenated by conventional processes. Products which
are wholly or partly hydrogenated in this way are superior to
non-hydrogenated polymers in that they possess improved resistance to
aging and are particularly resistant to oxidative degradation. In the case
of block copolymers of dienes and vinyl aromatic compounds, in particular,
the hydrogenated products also show improved tensile properties and
mechanical strength. When only partially hydrogenated, the diene polymers
may be vulcanized. Such vulcanizates possess a higher tensile strength and
a lower glass temperature than vulcanizates of non-hydrogenated diene
polymers.
U.S. Pat. No. 3,625,927 (Yoshimoto et al, Dec. 7, 1971) relates to a
catalyst for hydrogenating a high molecular weight polymer having
hydrogenatable unsaturated bonds. This catalyst is suitable for
hydrogenation of the polymer is a viscous solution form and comprises a
reaction product of (1) a metal chelate compound of nickel, cobalt, or
iron, with (2) an organic metallic reducing agent in said chelate
compound. The chelating agent is attached to the metal by a pair of
nitrogen atoms and an oxygen atom.
U.S. Pat. No. 3,531,450 (Yoshimoto et al, Sep. 29, 1970) relates to a new
hydrogenation catalyst consisting of three catalytic components and a
process for hydrogenating polymers by the use of said catalyst. This
three-component catalyst consists of (1) at least one kind of an
unsaturated hydrocarbon selected from the group consisting of an
olefinically unsaturated hydrocarbon and an acetylenically unsaturated
hydrocarbon, (2) at least one kind of an organic compound of the metal
selected from the group consisting of nickel, cobalt and iron, and (3) at
least one kind of a metal compound reducing agent.
U.S. Pat. No. 3,766,300 (De La Mare, Oct. 16, 1973) discloses a process for
the hydrogenation of copolymers prepared from conjugated dienes and
certain copolymerizable polar monomers such as vinyl pyridines,
acrylonitriles, and alpha-olefin oxides which comprises an initial step of
forming a complex between at least one Lewis acid and the polar portions
of the copolymer and thereafter subjecting the complex to hydrogenation.
More particularly, this reference is especially concerned with a process
for the hydrogenation of block copolymers derived from these monomers.
Japanese Patent 13,615 (Aug. 2, 1967; filed Feb. 15, 1963) relates to
copolymers of butadiene and vinyl pyridine that were reduced to give
waterproof, stable reduced copolymers. These products were useful for
coating pills. The reduced copolymers were obtained by the catalytic
hydrogenation in the presence of Raney nickel catalyst.
A paper titled "Oil-Resistant Rubbers from 2-Methyl Vinyl Pyridine," James
E. Pritchard and Milton H. Opheim, Industrial and Engineering Chemistry,
Volume 46, No. 10, pages 2242-2245, relates to quaternization of liquid
polymers. Copolymers of butadiene and 2-methyl-5-vinyl pyridine (MVP)
react with quaternizing agents to form polymeric salts of the type:
##STR1##
where R is an aliphatic or aromatic radical and X represents halide, alkyl
sulfate, or aryl sulfonate groups.
In addition, commercially available fluoroelastomers are synthesized by the
copolymerization of fluoro olefins, for example
##STR2##
Due to the saturated backbone and presence of carbon fluorine bonds, the
fluoro polymers have high thermooxidative stability when compared to their
hydrocarbon counterparts. The major drawback of these fluoro elastomers is
their poor low temperature properties which is reflected in relatively
high glass transition temperatures (Tg). The Tg's of oil-resistant
non-fluorinated elastomers are lower. Nitrile (i.e.,
butadiene/acrylonitrile copolymer with 40 weight percent acrylonitrile)
and hydrogenated nitrile rubber exhibit Tg's of about minus 30.degree. C.
versus a Tg of minus 20.degree. C. for the fluorinated copolymer described
above.
Elastomers derived from the copolymerization of fluorinated olefins with
hydrocarbon olefins are also heat resistant due to the saturated backbone
in these polymers. However, the lower the fluorine content, the lower the
heat and oil resistance. Also, the glass transition temperature of these
elastomers is not significantly improved when compared with the
corresponding highly fluorinated counterparts.
When a hydrocarbon diene such as 1,3-butadiene bears a fluorinated
substituent such as 2-trifluoromethyl, elastomeric homopolymers are
obtained. Free radical polymerization can occur in a 1,2; 3,4; or 1,4
manner. Polymerization in the latter mode would lead to backbone
unsaturation in the polymer, which is detrimental to the thermooxidative
stability of the polymer, more so than the pendant unsaturation generated
by polymerization in a 1,2- or 1,4- manner. Elastomeric polymers are also
obtained when the hydrogen atoms of 1,3-butadiene are substituted with
fluorine atoms (e.g., polyfluoroprene). However, these polymers also
suffer from poor thermooxidative instability due to the presence of
backbone unsaturation. Thermooxidative stability is increased in polymers
derived from highly fluorinated 1,3-dienes, but these materials tend to be
plastics.
Highly fluorinated 1,3-dienes can be copolymerized in emulsion with
1,3-diene hydrocarbons. Relatively low Tg materials can thus be obtained.
For example, a copolymer of 1,1,2-trifluorobutadiene with butadiene in a 1
to 1 mole ratio has a Tg of minus 48.degree. C.
U.S. Pat. No. 3,308,175 (Barr, Mar. 7, 1967) relates to novel
fluorine-substituted dienes, to a method for the preparation thereof, to
certain novel intermediates and the preparation thereof, and to certain
novel intermediates for the production of homologous fluorine-substituted
dienes.
U.S. Pat. No. 3,379,773 (Barr, Apr. 23, 1968) relates to polymeric
compositions and to processes for the preparation of those compositions.
Copolymers of 1,1,2-trifluorobutadiene-1,3 and the method of preparing the
same are described within this reference along with comonomers
hexafluorobutadiene-1,3; 3,4-dichloro-3,4,4-trifluorobutene-1;
2,2,2-trifluoroethyl vinyl ether; vinyl chloride; styrene;
1,1,2-trifluorobutene-1; and 1,1,4,4-tetrafluorobutadiene-1,3.
U.S. Pat. No. 3,398,128 (Bolstad et al, Aug. 20, 1968) relates to
halogen-containing copolymers of 1,1,2-trifluorobutadiene-1,3 and another
fluorinated 1,3-diene having from 4 to 5 carbon atoms per molecule
containing two fluorine atoms on a terminal carbon atom and at least one
hydrogen atom and the process for copolymerization of those monomers to
produce such copolymers.
U.S. Pat. No. 3,562,341 (Tarrant et al, Feb. 9, 1971) relates to
incompletely polyfluorinated 1,3-dienes capable of forming crosslinked
polymers and having fluorine substituents in at least the 1,1,2-position,
and to synthesis for their preparation. More particularly, this reference
relates to a synthesis for 1,1,2-trifluorobutadiene-1,3 and to the
compounds 1,1,2,4,4-pentafluorobutadiene-1,3, and
1,1,2,4,4-pentafluoro-3-methylbutadiene-1,3.
U.S. Pat. No. 3,607,850 (Smith, Sep. 21, 1971) relates to a method of
polymerizing conjugated fluorinated dienes which are rubber-like, flexible
at low temperatures, and resistant to mineral oils and other chemicals.
More particularly, the reference relates to use of rhodium salts or
complexes as catalysts for the polymerization or copolymerization of
conjugated fluorinated dienes to produce high molecular weight elastomers.
SUMMARY OF THE INVENTION
Random copolymer compositions which function as oil-resistant elastomers
are prepared by the emulsion polymerization of two monomeric classes. The
first monomeric class consists of a conjugated diene, or branched
conjugated diene, or mixtures thereof, containing from 4 to 8 carbon
atoms. The second monomeric class is characterized by general Formula I
##STR3##
or by general Formula II:
CH.sub.2 .dbd.CR.sub.8 CX (II)
With regard to Formula I, R.sub.1 is an alkenyl group containing from about
2 to about 8 carbon atoms, and R.sub.2 is hydrogen or an alkyl group
containing from 1 to about 8 carbon atoms. The second monomeric class can
be replaced with up to about 20 percent by weight of CH.sub.2
.dbd.CR.sub.3 CX wherein R.sub.3 is hydrogen or methyl and X is
--OOR.sub.4, --ONR.sub.5 R.sub.6 or OOR.sub.7 OR.sub.4 wherein R.sub.4 is
an alkyl group containing from 1 to about 4 carbon atoms, --CH.sub.2
CF.sub.3 or --CH.sub.3 CF.sub.2 CF.sub.2 H, R.sub.5 and R.sub.6 are alkyl
groups independently containing from 1 to about 4 carbon atoms and R.sub.7
is an alkylene group containing from 1 to about 4 carbon atoms. The random
copolymer so formed is then hydrogenated using a transition metal catalyst
and at least one complexing agent.
With regard to Formula II, R.sub.8 is hydrogen or an alkyl group containing
from 1 to about 4 carbon atoms and X is --OOR.sub.9, --ONR.sub.10 R.sub.11
or --OOR.sub.12 OR.sub.9 wherein R.sub.9 is an alkyl group containing from
1 to 4 carbon atoms, --CH.sub.2 CF.sub.3, or --CH.sub.2 CF.sub.2 CF.sub.2
H, R.sub.10 and R.sub.11 are alkyl groups independently containing from 1
to about 4 carbon atoms and R.sub.12 is an alkylene group containing from
1 to about 4 carbon atoms. Mixtures of this second monomeric class may
also be employed. The second monomeric class can be replaced with up to
about 20 percent by weight of
##STR4##
where R.sub.13 is an alkenyl group containing from about 2 to about 8
carbon atoms and R.sub.14 is hydrogen or an alkyl group containing from 1
to about 8 carbon atoms. The random copolymers so formed is then
hydrogenated using a transition metal catalyst and at least one complexing
agent.
In addition, fluorinated copolymers which function as oil resistant
elastomers are prepared by emulsion copolymerization of two monomer
classes. The first monomer comprises a fluorodiene of the structure
##STR5##
wherein substituent a is independently hydrogen or fluorine, R.sub.15 is
hydrogen or a fluoro alkyl group containing from 1 to about 4 carbon atoms
and containing at least three fluoro atoms, with the proviso that both
R.sub.15 groups are not hydrogen, R.sub.16 and R.sub.17 are independently
fluorine, hydrogen or a fluoro alkyl group containing from 1 to about 4
carbon atoms and containing at least three fluorine atoms.
The second monomer is (a) a hydrocarbon diene comprising a straight chain
conjugated diene, a branched conjugated diene or mixtures thereof
containing from 4 to about 8 carbon atoms, or a monomer(b), (b) being a
monomer of the general formula CH.sub.2 =CR.sub.18 X wherein R.sub.18 is
hydrogen or an alkyl group containing from 1 to about 4 carbon atoms, and
X is 2-pyridyl, 4-pyridyl, --COOR.sub.19, --CONR.sub.20 R.sub.21 or
--COOR.sub.22 OR.sub.19 wherein R.sub.19 is an alkyl group containing from
1 to about 4 carbon atoms, --CH.sub.2 CF.sub.3 or --CH.sub.2 CF.sub.2
CF.sub.2 H, R.sub.20 and R.sub.21 are alkyl groups containing from 1 to
about 4 carbon atoms, and R.sub.22 is an alkylene group containing from 1
to about 4 carbon atoms. The second monomer may also comprise a mixture of
monomers (a) and (b). The mole ratio of diene (a): CH.sub.2 .dbd.CR.sub.18
X (b), when (b) is present, is from 1:7 to about 7:1 and wherein the mole
ratio of first monomer:second monomer is from about 4:3 to about 2:3.
The copolymer so formed is then hydrogenated using a transitional metal
catalyst and a complexing agent and the transitional metal catalyst is
deactivated after hydrogenation by using a second complexing agent, in the
absence of air.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a graph of the proton magnetic resonance spectrum of the
unhydrogenated butadiene/2-vinylpyridine copolymer;
FIG. 2 is a graph of the proton magnetic resonance spectrum of the
hydrogenated butadiene/2-vinylpyridine copolymer;
FIG. 3 is a graph of the infrared spectrum of the unhydrogenated
butadiene/2-vinylpyridine copolymer;
FIG. 4 is a graph of the infrared spectrum of the hydrogenated
butadiene/2-vinylpyridine copolymer;
FIG. 5 is a graph of the proton magnetic resonance spectrum of the
hydrogenated butadiene/methyl acrylate copolymer;
FIG. 6 is a graph of the infrared spectrum of the unhydrogenated
butadiene/methyl acrylate copolymer;
FIG. 7 is a graph of the infrared spectrum of the hydrogenated
butadiene/methyl acrylate copolymer;
FIG. 8 is a graph of the proton magnetic resonance spectrum of the
unhydrogenated butadiene/2-methoxyethyl acrylate copolymer;
FIG. 9 is a graph of the proton magnetic resonance spectrum of the
hydrogenated butadiene/2-methoxyethyl acrylate copolymer;
FIG. 10 is a graph of the infrared spectrum of the unhydrogenated
butadiene/2-methoxyethyl acrylate copolymer;
FIG. 11 is a graph of the infrared spectrum of the hydrogenated
butadiene/2-methoxyethyl acrylate copolymer;
FIG. 12 is a graph of the proton magnetic resonance spectrum of the
unhydrogenated 1,1,2-trifluorobutadiene/1,3-butadiene copolymer; and
FIG. 13 is a graph of the proton magnetic resonance spectrum of the
hydrogenated 1,1,2-trifluorobutadiene/butadiene copolymer.
DETAILED DESCRIPTION OF THE INVENTION
This invention deals with compositions and a method for preparing high
temperature, oil-resistant elastomers by the copolymerization of two
monomeric classes followed by the hydrogenation of the copolymer. Direct
polymerization of ethylene with acrylonitrile to give HNBR is not feasible
due to the difference in reactivities of the monomers under the
copolymerization conditions. This is generally true in the case of
copolymerization of ethylene with any polar alpha, beta unsaturated
monomer. Direct copolymerization of ethylene and polar alpha, beta
unsaturated monomers (including acrylonitrile) using transition metal
catalysts have been unsuccessful.
Free radical polymerization at very high pressures, ca 2000 atmospheres,
results in comparable reactivity for ethylene and acrylonitrile, but the
polymerization process is plagued with side reactions that preclude high
molecular weight polymer formation. The polymer obtained thus is a poor
candidate for crosslinking to an elastomer.
Free radical polymerization can be performed at lower pressure, ca 60
atmospheres, in a solvent using a Lewis acid as the complexing agent for
the polar monomer, acrylonitrile. As an almost perfectly alternating
copolymer is formed, the low temperature properties are poorer than the
corresponding random copolymer. Also, tensile strength is reduced in the
perfectly alternating copolymer, due to the lack of polyethylene segments
which is responsible for the high strength of the random copolymer.
Conjugated dienes readily copolymerize with polar alpha, beta monomers in
emulsion to give high molecular weight copolymers. Subsequent
hydrogenation of the backbone unsaturation in these polymers is an
alternate route to copolymers of ethylene with polar alpha, beta
unsaturated monomers.
The first monomeric class is a straight chain conjugated diene, a branched
chain conjugated diene, or mixtures thereof. This diene contains from 4 to
8 carbon atoms. Examples of straight chain dienes are 1,3-butadiene,
1,3-pentadiene, 1,3-hexadiene, 1,4-hexadiene, 1,3-heptadiene,
2,4-heptadiene, 1,3-octadiene, 2,4-octadiene, and 3,5-octadiene. Some
representative examples of branched chain dienes are isoprene,
2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-hexadiene,
3-methyl-1,3-hexadiene, 2-methyl-2,4-hexadiene, 3-methyl-2,4-hexadiene,
2,3-dimethyl-1,3-pentadiene, 2,4-dimethyl-1,3-pentadiene,
2-ethyl-1,3-pentadiene, and 3-ethyl-1,3-pentadiene. The preferred dienes
for the practice of this invention are butadiene and isoprene.
In a first embodiment of the present invention, the second monomeric class
is of the general formula:
##STR6##
and in a second embodiment, the second monomeric class is of the general
formula:
CH.sub.2 .dbd.CR.sub.8 CX (II)
With regard to Formula I of the first embodiment, R.sub.1 is an alkenyl
group containing from about 2 to about 8 carbon atoms, preferably from
about 2 to 6, and most preferably from 2 to about 4 carbon atoms.
Particularly, R.sub.1 is vinyl. R.sub.2 is hydrogen or an alkyl group
containing from 1 to about 8 carbon atoms. When R.sub.2 is an alkyl group,
it preferably contains from 1 to about 6 carbon atoms and most preferably
from 1 to about 4 carbon atoms. When R.sub.2 is alkyl, a particular group
is methyl.
The general formula (I) of the second monomeric class can be replaced with
up to about 20 percent by weight of general formula IA
CH.sub.2 .dbd.CR.sub.3 CX (IA)
R.sub.3 is hydrogen or methyl and X is --OOR.sub.4, --ONR.sub.5 R.sub.6 or
--OOR.sub.7 OR.sub.4 wherein R.sub.4 is an alkyl group containing from 1
to about 4 carbon atoms, --CH.sub.2 CF.sub.3 or --CH.sub.2 CF.sub.2
CF.sub.2 H, R.sub.5 and R.sub.6 are alkyl groups independently containing
from 1 to about 4 carbon atoms and --OOR.sub.7 OR.sub.4 is an alkylene
group containing from 1 to about 4 carbon atoms. When R.sub.3 is hydrogen
or methyl and X is --OOR.sub.4, some examples of general formula IA are
acrylates, methacrylates, fluorinated acrylates or fluorinated
methacrylates. When R.sub.3 is hydrogen or methyl and X is ---ONR.sub.5
R.sub.6, general formula IA may be tertiary acrylamides or tertiary
methacrylamides. When X is --OOR.sub.7 OR.sub.4, preferably R.sub.7 is an
alkylene group containing from 1 to about 2 carbon atoms and R.sub.4 is an
alkyl group containing from 1 to about 2 carbon atoms. Preferably at least
3 percent of general formula (IA) is present in the second monomeric class
and most preferably at least 7 percent of general formula (IA) is present
in the second monomeric class.
In the second embodiment, the second monomeric class is of the general
formula:
CH.sub.2 .dbd.CR.sub.8 CX (II)
wherein R.sub.8 is hydrogen or an alkyl group containing from 1 to about 4
carbon atoms and X is --OOR.sub.9, --ONR.sub.10 R.sub.11 or --OOR.sub.12
OR.sub.9 wherein R.sub.9 is an alkyl group containing from 1 to about 4
carbon atoms, --CH.sub.2 CF.sub.3, or --CH.sub.2 CF.sub.2 CF.sub.2 H,
R.sub.10 and R.sub.11 are alkyl groups independently containing from 1 to
about 4 carbon atoms and R.sub.12 is an alkylene group containing from 1
to about 4 carbon atoms. Preferably R.sub.8 is hydrogen or an alkyl group
containing from 1 to 2 carbon atoms and most preferably R.sub.8 is
hydrogen or methyl. When X is --OOR.sub.9, R.sub.9 preferably is an alkyl
group containing from 1 to 2 carbon atoms, most preferably R.sub.9 is
methyl. When X is --ONR.sub.10 R.sub.11, preferably R.sub.10 and R.sub.11
are alkyl groups independently containing from 1 to 2 carbon atoms and
most preferably R.sub.10 and R.sub.11 are methyl. When X is --OOR.sub.12
OR.sub.9 preferably R.sub.12 is an alkylene group containing from 1 to
about 2 carbon atoms and R.sub.9 is an alkyl group containing from 1 to
about 2 carbon atoms.
When R.sub.8 is hydrogen or methyl and X is --OOR.sub.9, some examples of
general Formula II are acrylates, methacrylates, fluorinated acrylates, or
fluorinated methacrylates. When R.sub.8 is hydrogen or methyl and X is
--ONR.sub.10 R.sub.11, general Formula II may be tertiary acrylamides or
tertiary methacrylamides. When R.sub.8 is hydrogen or methyl and X is
--OOR.sub.12 OR.sub.9 general formula I may be alkoxyalkyl acrylates or
methacrylates.
The general Formula II of the second monomeric class can be replaced with
up to about 20 percent by weight of general Formula IIA
##STR7##
In general formula IIA, R.sub.13 is an alkenyl group containing from about
2 to about 8 carbon atoms and R.sub.14 is hydrogen or an alkyl group
containing from about 1 to about 8 carbon atoms. Preferably R.sub.13 is an
alkenyl group containing from about 2 to about 6 carbon atoms, and most
preferably from 2 to about 4 carbon atoms. Particularly, R.sub.13 is
vinyl. When R.sub.14 is an alkyl group, it preferably contains from 1 to
about 6 carbon atoms and most preferably from 1 to about 4 carbon atoms.
When R.sub.14 is alkyl, a particular group is methyl. Preferably at least
3 percent of general Formula IIA is present in the second monomeric class
and most preferably at least 7 percent of general Formula IIA is present
in the second monomeric class.
The hydrogenated random copolymers of the first two embodiments of this
invention have utility as high temperature oil-resistant elastomers. The
hydrogenated random copolymers of these embodiments may be solids or
liquids, depending on molecular weight. These hydrogenated random
copolymers serve as thermooxidatively stable oil resistant elastomers or
as impact modifiers for plastics. Products made from these elastomers find
use for seals, gaskets, and hoses. The liquid polymers can be used as
processing aids and/or modifiers in rubber and plastic compounding.
Conjugated 1,3-dienes copolymerize readily with alpha,beta unsaturated
monomers other than acrylonitrile. Examples of two such monomer classes
are vinyl pyridine or acrylates. These copolymers, like NBR, are also oil
resistant. In addition, hydrogenation of the polymer backbone together
with the pendant unsaturation derived from the hydrocarbon diene of the
conjugated diene/vinyl pyridine and conjugated diene/acrylate copolymers
is possible with inexpensive homogeneous catalysts based on iron, cobalt
or nickel by the process of the present invention. Hence, high temperature
oil resistant elastomer compositions of the present invention can be
obtained at a cost lower than that of HNBR.
The first step in the preparation of an oil-resistant elastomer is in
forming a random copolymer of the two monomeric classes. The random
copolymer is formed by emulsion polymerization. The weight ratio of the
first monomeric class:the second monomeric class is from about
25-85:75-15, preferably 40-60:60-40, and most preferably 55-60:45-40.
The random copolymer is made in a conventional manner. That is, the
above-noted monomers are added to suitable amounts of water in a
polymerization vessel along with one or more conventional ingredients and
polymerized. The amount of polymerized solids or particles is generally
from about 15 percent to about 50 percent with from about 25 to about 35
percent by weight being desired. The temperature of polymerization is
generally from about 5.degree. C. to about 80.degree. C. with from about
5.degree. C. to about 20.degree. C. being preferred. Typically in excess
of 60 percent and usually from about 70 percent to about 95 percent
conversion is obtained with from about 80 percent to about 85 percent
conversion being preferred. The polymerization is generally initiated by
free radical catalysts which are utilized in conventional amounts.
Examples of such catalysts include organic peroxides and hydroperoxides
such as benzoyl peroxide, dicumyl peroxide, cumene hydroperoxide,
paramenthane hydroperoxide, and the like, used alone or with redox
systems; diazo compounds such as dimethyl 2,2'-azobisisobutyrate, and the
like; persulfate salts such as sodium, potassium, and ammonium persulfate,
used alone or with redox systems; and the use of ultraviolet light with
photo-sensitive agents such as benzophenone, triphenylphosphine, organic
diazos, and the like.
Inasmuch as the random copolymers are prepared via an emulsion latex
polymerization route, anionic emulsifying aids are utilized. Thus, various
conventional anionic surfactants known to the art as well as to the
literature are utilized. Generally, any suitable anionic surfactant can be
utilized such as those set forth in McCutcheons, "Detergents and
Emulsifiers," 1978, North American Edition, Published by McCutcheon's
Division, MC Publishing Corp., Glen Rock, N.J., U.S.A., as well as the
various subsequent editions thereof, all of which are hereby fully
incorporated by reference. Desirably, various conventional soaps or
detergents are utilized such as a sodium alkyl sulfate, wherein the alkyl
group has from 8 to 22 carbon atoms such as sodium lauryl sulfate, sodium
stearyl sulfate, and the like, as well as various sodium alkyl benzene
sulfonates, wherein the alkyl group has from 8 to 22 carbon atoms such as
sodium dodecyl benzene sulfonate, and the like. Other anionic surfactants
include sulfosuccinates and disulfonated alkyl benzene derivatives having
a total of from 8 to 22 carbon atoms. Various phenyl type phosphates can
also be utilized. Yet other anionic surfactants include various fatty acid
salts having from 12 to 22 carbon atoms as well as various rosin acid
salts wherein the salt portion is generally lithium, sodium, potassium,
ammonium, magnesium, and the like. The selection of the anionic surfactant
generally depends on the pH of the polymerization reaction. Hence, fatty
acid salts and rosin acid salts are not utilized at low pH values.
The amount of the surfactant can vary depending upon the size of random
copolymer particles desired, but typically is from about 1 percent to
about 6 percent and desirably from about 2 percent to about 3 percent by
weight for every 100 parts by weight of the random copolymer forming
monomers.
Other anionic emulsifying aids are various anionic electrolytes which
control particle size by controlling the solubility of the soap. Examples
of various conventional electrolytes generally include sodium, potassium,
or ammonium naphthalene sulfonates. Other suitable electrolytes include
sodium sulfate, sodium carbonate, sodium chloride, potassium carbonate,
sodium phosphate, and the like. The amount of electrolyte is generally
from about 0.1 to about 1.0 parts by weight and preferably from about 0.2
to about 0.5 parts by weight for every 100 parts by weight of the random
copolymer forming monomers.
Molecular weight modifiers are also utilized to maintain the molecular
weight within desirable limits as otherwise the viscosity of the polymer
would be exceedingly high for subsequent handling, processing, and the
like. Generally, known conventional molecular weight modifiers can be
utilized such as various mercaptans which have from about 8 to about 22
carbon atoms, generally in the form of an alkyl group. Various sulfide
compounds can also be utilized such as diisopropylxanthogendisulfide and
di-sec-butylxanthogendisulfide. The amount of the molecular modifiers is
generally an effective amount such that the Mooney viscosity, that is
ML.sub.4 @100.degree. C. is from about 10 to about 120 and desirably from
about 20 to about 80.
Yet another conventional emulsion latex additive is various short stop
agents which are added generally to stop the polymerization and to tie up
and react with residual catalysts. The amount of the short stop agents is
from about 0.05 to about 1.0 parts by weight per 100 parts by weight of
said random copolymer forming monomers. Examples of specific short stop
agents include hydroxyl ammonium sulfate, hydroquinone and derivatives
thereof, e.g., ditertiaryamylhydroquinone, various carbamate salts such as
sodium diethyldithiocarbamate, various hydroxyl amine salts, and the like.
Various antioxidants can be added and such are known to the art as well as
to the literature including various phenolic type antioxidants such as
di-tert-butyl-paracresol, various diphenylamine antioxidants such as
octylated diphenylamine, various phosphite antioxidants such as trisnonyl
phenyl phosphite, and the like. Once the short stop has been added to the
latex solution, excess monomer is stripped from the resultant latex, as
for example by steam.
A cationic coagulant polymer is utilized to coagulate the anionic
emulsifying aids such as the various anionic surfactants and the various
anionic electrolytes utilized. Polymeric cationic type coagulants are
utilized according to the present invention inasmuch as they have a
positive site which generally reacts with the negative or anionic site of
the surfactant, electrolyte, etc., and thereby neutralize the same and
render it innocuous. That is, according to the concepts of the present
invention, the anionic emulsifying aids are not physically removed but
rather are chemically reacted with a cationic polymeric coagulant to form
an adduct which is generally dispersed throughout the random copolymer
particle.
Large stoichiometrically equivalent amounts of cationic polymeric
coagulants are utilized. That is, large weight equivalents are required in
order to yield a random copolymer having improved properties. Generally,
from about 0.75 to about 1.5 weight equivalents, desirably from about 0.85
to about 1.25, and preferably from about 0.95 to about 1.05 weight
equivalents of the cationic polymeric coagulant is utilized for every
weight equivalent of said anionic emulsifying aids. Equivalent weight
amounts less than those set forth herein do not result in effective
neutralization, tying up, or negate the effect which the various anionic
emulsifying aids have upon the properties of the dried rubber particles.
The cationic polymeric coagulants utilized in the present invention
generally contain a tetravalent nitrogen and are sometimes referred to as
polyquats. This invention Cationicity of the quaternary nitrogen is
generally independent of pH, although other parts of the polymer molecule
may exhibit sensitivity to pH such as hydrolysis of ester linkages.
Typically, cationic polymers are prepared either by quaternization of
poly(alkylene polyamines), poly(hydroxyalkylene polyamines), or
poly(carbonylalkylene polyamine) with alkyl halides or sulfates, or by
step-growth polymerization from dialkylamines, tetraalkyl amines, or
derivatives thereof, with suitable bifunctional alkylating agents, and
with or without small amounts of polyfunctional primary amines (such as
ammonia, ethylene diamines, and others) for molecular weight enhancement.
Polyamines produced from ammonia and ethylene dichloride, quaternized with
methyl chloride, and polyquaternaries produced directly from dimethylamine
and 1-chloro-2,3-epoxypropane are generally of commercial significance.
Epichlorohydrin reacts with ammonia and primary, secondary, or
polyfunctional amines to form polyamines or polyquats. The polyamines can
be subsequently quaternized to yield a cationic polymeric coagulant of the
present invention. As known to those skilled in the art and to the
literature, literally hundreds of cationic polymeric coagulants exist and
generally the same can be utilized in the present invention. Examples of
specific polymeric cationic coagulants include
poly(2-hydroxypropyl-1-N-methylammonium chloride),
poly(2-hydroxypropyl-1,N,N-dimethylammoniumchloride),poly(diallyldimethyla
mmonium chloride), poly(N,N-dimethylaminoethyl methacrylate) quaternized,
and a quaternized polymer of epichlorohydrin and a dialkylamine wherein
the alkyl group has from 1 to 5 carbon atoms with methyl being preferred.
The method of preparing cationic polymeric coagulants, general types of
such compounds as well as specific individual compounds are set forth in
the following documents which are hereby fully incorporated by reference
with regard to all aspects thereof:
Encyclopedia of Polymer Science and Technology, John Wiley & Sons, New
York, 1987, Volume 11, 2nd Edition, pages 489-503.
Encyclopedia of Polymer Science and Technology, John Wiley & Sons, New
York, 1987, Volume 7, 2nd Edition, pages 211-229.
Kirk Othermer's Encyclopedia of Chemical Technology, 3rd Edition, Volume
10, John Wiley & Sons, New York, 1980, pages 489-523.
A text entitled Commercial Organic Flocculants, Josef Vostrcil and
Frantisek Juracka, Noyes Data Corporation, Park Ridge, N.J., 1976, in its
entirety.
The cationic polymeric coagulants utilized in the first two embodiments of
the present invention generally have a molecular weight of from about
1,000 to about 10,000,000.
According to the first two embodiments of the present invention, the
cationic polymeric coagulant treated random copolymer latex generally
results in a slurry of rubber crumbs in a clear aqueous liquid. The crumbs
contain the various anionic emulsifying aids physically incorporated
therein. Such crumbs can be separated in any conventional manner as by
filtering. Inasmuch as the anionic emulsifying aids have been rendered
innocuous, multiple washing steps or other expensive, tedious process
steps such as solvent extraction are not utilized.
The random copolymers of the first two embodiments of the present invention
once dried as by conventional means, have improved properties such as good
water resistance, good adhesion properties, non-interference with cure
systems when cured, reduce fouling of molds during the manufacture of
parts, improved electrical insulating properties, and the like. Such
polymers can accordingly be utilized as adhesives, that is polymeric
adhesives, binders, films, e.g., electrical insulating films, coatings
such as for electrical circuit boards along with other conventional
coating additives and fillers known to the art and to the literature, and
the like. Suitable adhesive uses include metal-to-metal adhesion,
metal-to-fabric adhesion, metal-to-plastic adhesion, and the like.
Additionally, the polymers of the first two embodiments of this invention
have utility in the automotive area such as in hoses, gaskets, seals, and
timing belts.
The random copolymers can be prepared with a mercaptan chain transfer agent
composition comprising (a) at least one mercaptan chain transfer agent and
(b) at least one non-polymerizable material which is miscible with the
mercaptan chain transfer agent. Suitable mercaptans include water soluble
mercaptans such as 2-mercaptoethanol, 3-mercaptopropanol,
thiopropyleneglycol, thioglycerine, thioglycolic acid, thiohydracrylic
acid, thiolactic acid, and thiomalic acid, and the like. Suitable
non-water soluble mercaptans include isooctyl thioglycolate, n-butyl
3-mercaptopropionate, n-butyl thioglycolate, glycol dimercaptoacetate,
trimethylolpropane trithioglycolate, alkyl mercaptans, and the like. The
preferred mercaptans are 2-mercaptoethanol and t-dodecylmercaptan,
however, any chain transfer agent having a mercapto (--SH) group would be
acceptable.
The chain transfer composition, in addition to the mercaptan, may contain
at least one non-polymerizable material which is miscible with the
mercaptan and is substantially insoluble in water. The term
nonpolymerizable as used herein means that the material does not form a
part of the random copolymer chain in the sense that a traditional
comonomer would form. The non-polymerizable material may, in some cases,
graft polymerize onto the random copolymer chain but this is not normally
considered a copolymer. The term substantially insoluble in water as used
in this specification means that the material has less than 5 percent
solubility in water. The non-polymerizable material may be a monomer,
oligomer or a polymer. Suitable nonpolymerizable materials include dioctyl
phthalate, low molecular weight poly(caprolactone), polysilicones, esters
of glycerols, polyesters, water insoluble esters of fatty acids with --OH
terminated polyoxyethylene and polyoxypropylene, esters of polyols, esters
of monoacids and polyacids, esters of organic polyphosphates, phenyl
ethers, ethoxylated alkylphenols, sorbitan monostearate and sorbitan
monooleate and other sorbitol esters of fatty acids. The choice of
material is not critical as long as the material is non-polymerizable with
the monomers and is substantially insoluble in water.
The chain transfer composition must contain at least enough
non-polymerizable material to encapsulate the mercaptan chain transfer
agent. This amount varies according to the type and amount of chain
transfer agent used. Usually, the chain transfer composition must contain
at least an equal amount in weight of non-polymerizable material as chain
transfer agent in order to encapsulate or host the chain transfer agent.
Preferably, the composition contains at least twice as much weight of
non-polymerizable material as chain transfer agent. Other non-essential
ingredients may be used in the chain transfer compositions of this
invention but are not preferred.
The chain transfer compositions are formed by mixing the two essential
ingredients together. The method used to mix the ingredients is not
critical and may be any of the known methods used by those skilled in the
art. The ingredients may even be charged to the polymerization reactor and
mixed before adding the other polymerization ingredients but is preferably
mixed outside the reactor.
Because of the detrimental effects that mercaptans, such as
2-mercaptoethanol have on colloidal stability, it is necessary to mix the
2-mercaptoethanol with the non-polymerizable material before adding it to
the reaction medium. The non-polymerizable material serves as a host
material for the chain transfer agent. This procedure surprisingly
eliminates the adverse effects of 2-mercaptoethanol on colloidal
stability. It is believed that the non-polymerizable material averts the
adverse effect of 2-mercaptoethanol on colloidal stability via
encapsulation, complexation or interaction and, thus, allows relatively
high levels of 2-mercaptoethanol to be introduced to the reaction medium
prior to the start of polymerization. The term "encapsulation" as used
herein is not intended as the traditional meaning of encapsulation which
is to coat or contain and the result is a heterogeneous system. The chain
transfer composition of this invention is homogeneous.
The level of chain transfer composition used to make the random copolymer
will be described in terms of the level of mercaptan in the composition.
The level of mercaptan used is greater than 0.03 part by weight per 100
parts by weight of diene monomer. The preferred levels of mercaptan range
from about 0.03 to about 5.00 parts by weight per 100 parts of monomer,
and, preferably, from 0.10 to 1.50 parts.
When high amounts of mercaptan, such as 2-mercaptoethanol, are used, it is
desirable to not charge the entire amount of chain transfer agent at the
beginning of polymerization since 2-mercaptoethanol has a diminishing
effect on molecular weight above about the 1.5 parts level. Therefore, if,
for example, 3.0 parts were used, it would be advisable to add only up to
1.5 parts at the beginning of polymerization and to gradually add the
remainder during polymerization. Amounts added at the beginning which are
greater than 1.5 parts do not result in colloidal instability. However,
for the most efficient use of chain transfer agent, it is preferred to not
add more than 1.5 parts before the beginning of polymerization. This
preferred initial level could, of course, be different for different
mercaptans. The above described preferred procedure is for
2-mercaptoethanol.
If less than 0.25 part by weight of chain transfer agent is used, then all
of the chain transfer agent will be added in the form of the chain
transfer composition before the beginning of polymerization. If more than
0.25 part is used, then at least 0.25 part will be added in the form of
the chain transfer composition before the beginning of polymerization and
the remainder may be added later. To gain the most efficiency of the chain
transfer agent, no more than 1.5 parts by weight should be added before
the start of polymerization. For best results, at least 50 percent of the
chain transfer agent, preferably 100 percent, is added to the
polymerization medium prior to the start of polymerization. Any amount not
added at the start and not encapsulated should be added after the
polymerization has reached about 10 percent conversion to maintain
colloidal stability. Except for the use of the chain transfer composition,
the polymerization is much the same as in any conventional polymerization
of a diene monomer in an aqueous medium.
Another class of chain-transfer agents that are used in the process of the
first two embodiments of this invention are mercapto organic compounds
having at least one ether linkage that have the structural formula
X--(CH.sub.2).sub.m --(OY).sub.n --SH
wherein X represents hydrogen or --SH, Y represents an alkylene group
having 1 to 6 carbon atoms, and m and n each represents a number in the
range of 1 to 10.
A preferred group of ether linkage chain-transfer agents includes mercapto
organic compounds that have the structural formula
X--(CH.sub.2).sub.m '--(OY').sub.n '--SH
wherein X represents hydrogen or --SH, Y' represents an alkylene group
having 2 to 4 carbon atoms, and m' and n' each represents a number in the
range of 2 to 4.
Illustrative of the ether linkage chain-transfer agents that can be used in
the practice of this invention are the following compounds:
mercaptomethyl ethyl ether,
2-mercaptoethyl ethyl ether,
2-mercaptoethyl propyl ether,
2-mercaptoethyl butyl ether,
3-mercaptopropyl methyl ether,
3-mercaptopropyl ethyl ether,
3-mercaptopropyl butyl ether,
2-mercaptopropyl isopropyl ether,
4-mercaptobutyl ethyl ether,
bis-(2-mercaptoethyl) ether,
bis-(3-mercaptopropyl) ether,
bis-(4-mercaptobutyl) ether,
(2-mercaptoethyl) (3-mercaptopropyl) ether,
(2-mercaptoethyl)(4-mercaptobutyl) ether,
ethoxypolypropylene glycol mercaptan,
methoxypolyethylene glycol mercaptan,
and the like and mixtures thereof.
Among the preferred ether linkage chain-transfer agents are 2-mercaptoethyl
ethyl ether and bis-(2-mercaptoethyl) ether.
The amount of the ether linkage chain-transfer agent that is used in the
polymerization reaction is that which will provide a polymer having the
desired molecular weight or degree of polymerization. In most cases from
0.01 percent to 2 percent by weight, based on the weight of the monomer
component, is used. When a low molecular weight product that has a
relative viscosity in the range of 1.20 to 1.60 is desired, the amount of
chain transfer agent used is preferably in the range of 0.25 percent to
1.75 percent by weight, based on the weight of the monomer. Amounts in the
range of 0.05 percent to 0.15 by weight, based on the weight of the
monomer, are preferably used to produce polymers having high molecular
weights.
The random copolymers obtained in the first two embodiments of the present
invention generally have a weight average molecular weight of from about
20,000 to about 1,000,000; desirably from about 200,000 to about 750,000;
and preferably from about 400,000 to about 500,000.
The first two embodiments of the present invention will be better
understood by reference to the following examples.
EXAMPLE 1
First Embodiment
The below Table I shows the preparation of a random copolymer of butadiene
and 2-vinylpyridine. Items 1 through 9 are initially charged into a 15
gallon reactor under nitrogen and cooled to 5.degree. C. Polymerization is
initiated by adding items 10 through 12. These three items promote
peroxide breakdown thereby generating initiator radicals. The conversion
is monitored by measuring total solids content every hour. At 35 percent
conversion, the additional items 1 through 5 are added. After 20 hours, at
5.degree. C., 80 percent conversion is obtained and the reaction is
terminated by adding item 13. After removal of volatiles, the latex is
coagulated in hot water (70.degree. C.) containing 1.5 weight percent of
aluminum sulfate to form a crumb. The crumb is filtered, washed with water
and dried in air at 100.degree. C. for 4 hours.
TABLE I
__________________________________________________________________________
Parts by Weight
Added Added at
Item
Material Purity %
Initially
35% Conv.
Total
__________________________________________________________________________
1 Soft Water 100 186.48
12.83 199.31
2 Sipex SB emulsifier
30 2.0 1.0 3.0
3 Sodium Naphthalene
100 .67 .33 1.0
Sulfonate Secondary
Emulsifier
4 Sodium Carbonate
100 .16 .08 .24
Electrolyte
5 Sulfole 120 Chain
100 .18 .12 .30
Transfer Agent
6 Cumene Hydroperoxide
82.5 .115 -- .115
Initiator
7 Sodium Hydrosulfite
100 .007 -- .007
Oxygen Scavenger
8 Butadiene Monomer
100 45 -- 45
9 2-Vinylpyridine Monomer
100 45 -- 45
10 Trisodium Ethylenediamine
100 .01 -- .01
Tetraacetate Trihydrate
Complexing Agent for iron
salts
11 Sodium Ferric Ethylene
100 .015 -- .015
Diamine Tetraacetate
12 Sodium Formaldehyde
100 .105 -- .105
Sulfoxylate Reducing
Agent for Ferric Salts
13 Hydroxyl Ammonium
100 -- -- .3
Sulfate Short Stop
__________________________________________________________________________
EXAMPLES 2-5
First Embodiment
Examples 2 through 5 essentially follow the procedure of Example 1 except
for the monomers and level of monomers employed. Table II outlines
Examples 2 through 5.
TABLE II
______________________________________
Example
First Second Ratio of First
No. Monomer Monomer & Second Monomer
______________________________________
2 Butadiene 2-vinylpyridine
40:60
3 Isoprene 2-vinylpyridine
50:50
4 Isoprene 4-vinylpyridine
55:45
5 2,3-dimethyl
2-methyl-5-vinyl-
50:50
1,3-butadiene
pyridine + 3%
methyl-
methacrylate
______________________________________
The random copolymer obtained has a high cis-trans-1,4 microstructure
rather than 1,2 and/or 3,4 microstructure (depending upon the diene). The
combined mole percent of cis-trans 1,4-microstructure to vinyl
microstructure has been determined to be 3.7:1 by proton magnetic
resonance when the copolymers have a weight ratio of 60 percent butadiene
to 40 percent 2-vinylpyridine by weight. The cis and trans microstructure
get hydrogenated to linear polyethylene segments which are responsible for
the improved mechanical properties of the elastomer due to stretch
crystallinity (A. H. Weinstein, Rubber Chemical Technology 57, 203
(1984)).
EXAMPLE 6
Second Embodiment
The below Table III shows the preparation of a random copolymer of
butadiene and methyl acrylate. Items 1 through 9 are initially charged
into a 15 gallon reactor under nitrogen and cooled to 5.degree. C.
Polymerization is initiated by adding items 10 through 12. These three
items promote peroxide breakdown thereby generating initiator radicals.
The conversion is monitored by measuring total solids content every hour.
At 35 percent conversion, the additional items 1 through 5 are added.
After 20 hours, at 5.degree. C., 80 percent conversion is obtained and the
reaction is terminated by adding item 13. After removal of volatiles, the
latex is coagulated in hot water (70.degree. C.) containing 1.5 weight
percent of aluminum sulfate to form a crumb. The crumb is filtered, washed
with water and dried in air at 100.degree. C. for 4 hours.
TABLE III
__________________________________________________________________________
Parts by Weight
Added Added at
Item
Material Purity %
Initially
35% Conv.
Total
__________________________________________________________________________
1 Soft Water 100 186.48
12.83 199.31
2 Sipex SB emulsifier
30 2.0 1.0 3.0
3 Sodium Naphthalene
100 .67 .33 1.0
Sulfonate Secondary
Emulsifier
4 Sodium Carbonate
100 .16 .08 .24
Electrolyte
5 Sulfole 120 Chain
100 .18 .12 .30
Transfer Agent
6 Cumene Hydroperoxide
82.5 .115 -- .115
Initiator
7 Sodium Hydrosulfite
100 .007 -- .007
Oxygen Scavenger
8 Butadiene Monomer
100 50 -- 50
9 Methyl Acrylate
100 50 -- 50
Monomer
10 Trisodium Ethylenediamine
100 .01 -- .01
Tetraacetate Trihydrate
complexing agent for iron
salts
11 Sodium Ferric Ethylene
100 .015 -- .015
Diamine Tetraacetate
12 Sodium Formaldehyde
100 .105 -- .105
Sulfoxylate Reducing
Agent for Ferric Salts
13 Hydroxyl Ammonium
100 -- -- .3
Sulfate Short Stop
__________________________________________________________________________
EXAMPLES 7-10
Examples 7 through 10 essentially follow the procedure of Example 6 except
for the monomers and level of monomers employed. Table IV outlines
Examples 7 through 10.
TABLE IV
______________________________________
Example
First Second Ratio of First
No. Monomer Monomer & Second Monomer
______________________________________
7 Butadiene ethyl acrylate
40:60
8 Isoprene methyl 50:50
methacrylate
9 Isoprene methyl 55:45
acrylate + 3%
2-methyl-5-vinyl-
pyridine
10 2,3-dimethyl
N,N-dimethyl 50:50
1-3-butadiene
methacryl-
amide + 3% 4-
vinylpyridine
______________________________________
The random copolymer obtained has a high cistrans 1,4 microstructure rather
than 1,2 and/or 3,4 microstructure (depending upon the diene). The
combined mole percent of cis-trans 1,4-microstructure to vinyl
microstructure has been determined to be 3.7:1 by proton magnetic
resonance when the copolymers have a weight ratio of 50 percent butadiene
to 50 percent methyl acrylate. The cis and trans microstructure get
hydrogenated to linear polyethylene segments which are responsible for the
improved mechanical properties of the elastomer due to stretch
crystallinity (A. H. Weinstein, Rubber Chemical Technology 57, 203 (1984).
The random copolymer once obtained in either of the first two embodiments
of the invention described above is then subjected to hydrogenation in the
presence of a transition metal catalyst and trialkylaluminum catalyst in
the presence of at least one complexing agent and further in the absence
of BF.sub.3 or BF.sub.3 etherate.
Either a homogeneous or a heterogeneous catalyst may be used for the
hydrogenation although a homogeneous catalyst is preferred. Since a
homogeneous catalyst dissolves in solution, good contact is obtained with
the random copolymer. The homogeneous catalysts are transition metal
catalysts of either iron, cobalt, or nickel. These metals are present as
halides, acetates, or acetylacetonates. Most suitable are transition metal
salts that are soluble in the organic solvents used to dissolve the
polymeric substrates. These salts then yield a homogeneous zero or low
valent metallic species, which can be transformed efficiently under
hydrogen into a metal hydride species that is the active hydrogenation
catalyst. In general, the reduction of insoluble transition metal salts
cause the reduced metallic species to encapsulate the metal salt
substrate, thus preventing complete reduction. Transformation of this
heterogeneous reaction product to the active metal hydride is also then
inefficient. Thus, soluble transition metal salts are preferred such as
the octoates, neodecanoates, or stearates of cobalt or nickel. The least
hygroscopic of the abovementioned salts, namely the neodecanoates (due to
the bulky hydrophobic groups surrounding the metal ion), are most
preferred as water is detrimental to the formation of an active
hydrogenation catalyst. Other homogeneous catalysts that can be employed
are palladium, platinum or rhodium present as tetrakistriphenylphosphine
palladium (0), tetrakistriphenylphosphine platinum (0) or
tristriphenylphosphinerhodium chloride.
Conventional homogeneous catalysts based on, for example, reduced cobalt
salts are inexpensive compared to rhodium or palladium, but are only
suitable for the hydrogenation of hydrocarbon polymers, e.g., a nickel
catalyst is commercially used in the hydrogenation of Krayton, a triblock
butadiene-styrene-butadiene copolymer. Hydrogenation of the polymer
backbone of NBR is not possible using these catalysts, as the nitrile
group in NBR acts as a catalyst poison, and, in some cases is itself
reduced.
HNBR is commercially synthesized by the hydrogenation of NBR in solution.
The relatively high cost of HNBR compared to NBR is partly due to the
solution hydrogenation process, the major contribution to cost being the
catalyst (rhodium or palladium).
The transition metal catalyst is employed with trialkylaluminum compounds,
wherein the alkyl group contains from 1 to about 4 carbon atoms, which
functions as a reducing agent. Other reducing agents that can be employed
are dialkyl aluminum hydride, the dialkyl aluminum alkoxides of 1 to 4
carbon atoms, sodium borohydride, and lithium aluminum hydride.
Additionally, other reductants are alkyl lithium, dialkyl magnesium, and
alkyl magnesium halide wherein the alkyl groups are from 1 to 4 carbon
atoms, and the halide is chloride or bromide.
The mole ratio of transition metal catalyst: reducing agent is usually from
1:10, preferably 1:6, and most preferably from 1:4.
In accordance with one of the main features of the present invention, the
transition metal catalyst complexes with at least one complexing agent.
Without the complexing agent, addition of the catalyst to the polymer
solution causes gelation. This is due to crosslinking of the high
molecular weight copolymer caused by complexing of the polar groups with
the transition metal and metallic species from the reductant employed in
catalyst formation. The complexation is an equilibrium process wherein the
catalyst can be released into solution by the action of the solvent. In
high molecular weight copolymers, only one or two crosslinks per 200-300
monomer units are needed to form a gel or the like. Hence, in spite of the
low catalyst level, and catalyst equilibration into the solvent, at any
one time the condition for gel formation exists [H. F. Mark, J. Polymer
Sci.Applied Polymer Symposia, 39, 1 (1984)]. A gelled polymer is difficult
to hydrogenate to a high degree due to reduced catalyst mobility and
further due to inefficient contact between hydrogen, the catalyst, and the
sites of unsaturation derived from the copolymerized hydrocarbon diene.
Also, a partially crosslinked polymer results wherein the polar group may
undergo partial hydrogenation (see for example, U.S. Pat. No. 3,766,300).
Hydrogenation of the polar group would lower the oil resistance of the
elastomer. These factors cause the elastomer to be poorer in heat aging
and physical properties when compared to the polymers of this invention.
In the first two embodiments of the present invention the complexing
agents complex with the catalyst in order to prevent the catalyst from
excessively bonding to the pyridine rings in the first embodiment of the
invention or to the ester functionalities in the second embodiment. Thus,
catalyst mobility is improved. The complexing agent allows the catalyst to
break away from the polar groups of the polymer and to travel to the less
polar sites of unsaturation where hydrogenation should occur. These sites
of unsaturation compete efficiently enough for the catalyst (in comparison
to the catalyst complexing agent) in order to allow hydrogenation to
proceed.
In comparison, in U.S. Pat. No. 3,766,300, catalyst mobility is improved by
polymer modification. For example, all of the pyridine nitrogen atoms in a
butadiene-b-2-vinylpyridine copolymer were complexed with at least a
stoichiometric amount of a Lewis acid (e.g., BF.sub.3). The polymer thus
modified could be readily hydrogenated. Since the catalyst utilized in the
present invention comprises a very small portion (i.e., approximately 1
weight percent) when compared to the weight of the copolymer, it is much
more economical to modify the catalyst than the polymer itself as taught
in U.S. Pat. No. 3,766,300.
Thus, in accordance with one of the important aspects of the present
invention, unexpectedly high degrees of hydrogenation of the copolymer
unsaturated olefinic backbone and pendant unsaturation due to the
copolymerized hydrocarbon diene are achieved, which saturation improves
the heat resistance of the copolymers, without concomitant hydrogenation
of the polar groups of the copolymer which would lower the oil-resistance
of the copolymer, which is undesirable. Such unexpected results are
achieved through the use of the complexing agent for the hydrogenation
catalyst which prevents "poisoning" of the catalyst by the polar groups of
the copolymer thereby enabling the catalyst to complex with unsaturated
sites along the olefinic copolymer backbone to achieve the high levels of
hydrogenation thereof. The desired degree of hydrogenation of the
copolymers produced in the first two embodiments of the present invention
is greater than about 80 percent; desirably greater than about 85 percent;
and preferably greater than 95 percent hydrogenation of the unsaturation
derived from the copolymerized hydrocarbon diene.
The amount of complexing agent employed is related to the relatively low
catalyst level. Generally, the mole ratio of catalyst:complexing agent is
from 1:10, preferably 1:8; and most preferably 1:6. The complexing agents
for the catalysts are hexamethylphosphoric triamide,
tetramethylethylenediamine, phosphines of the general formula
(R.sub.23).sub.3 P, phosphites of the general formula (R.sub.23 O).sub.3 P
wherein R.sub.23 is an alkyl group containing from 1 to about 6 carbon
atoms, a phenyl group or a substituted aromatic group wherein the
substituent is an alkyl group containing from 1 to about 2 carbon atoms
such as o-tolyl.
Solvents for the hydrogenation are well known in the art. An exemplary list
of solvents are xylenes, toluenes, anisole, dioxane, tetrahydrofuran,
hydrocarbons such as hexanes, heptanes, and octanes and chlorinated
hydrocarbons such as chlorobenzene and tetrachloroethane, tri-substituted
amines such as triethylamine and tetramethylethylene diamine.
The temperature of hydrogenation is generally from about 25.degree. C. to
about 150.degree. C. with from about 25.degree. C. to about 50.degree. C.
being preferred.
Removal of the transition metal catalyst is difficult and expensive. This
is due to the high molecular weight of the polymer and also that the
catalyst is intimately associated with the polymer. A catalyst, when left
in contact with the hydrogenated polymer, shows a degradative action. This
action is discussed in a paper titled "Rule of Metals and Metal
Deactivators in Polymer Degradation," Z. Osawa, Polymer Degradation and
Stability, 20, 203 (1988). An approach of this invention was the partial
removal of the catalyst within the polymer, and also to render the
residual catalyst innocuous, that is, to deactivate the catalyst by the
addition of a second complexing agent after hydrogenation in the absence
of air. If the catalyst is not rendered innocuous, the polymer shows poor
heat aging and high oil swell. Some examples of the second complexing
agents are weak organic acids containing from 1 to about 4 carbon atoms
such as formic acid, acetic acid, and propionic acid; diacids containing
from 2 to about 6 carbon atoms such as oxalic acid, malonic acid, succinic
acid, glutaric acid, and adipic acid and also sodium or potassium salts of
the above mono- or diacids; trisodium ethylenediaminetetraacetate; amino
acids of 1 to about 4 carbon atoms such as glycine, alanine, alphaglutaric
acid, betaglutaric acid, and gammaglutaric acid; citric acid; pyridine or
substituted pyridine wherein the substituent contains 1 to 2 carbon atoms;
pyridine carboxylic acids such as nicotinic acid and the corresponding
sodium or potassium salts; alkyl or aromatic nitriles containing from 1 to
6 carbon atoms; substituted ureas or thioureas such as
N,N-dialkyldithiocarbamate metal salts of 1 to 4 carbon atoms wherein the
metal is lithium, sodium, or potassium; sodium or potassium salt of
dimethylglyoxime; hexamethylphosphoric triamide;
tetramethylethylenediamine; phosphines P(R.sub.24).sub.3 and phosphites
P(OR.sub.24).sub.3 wherein R.sub.24 is aliphatic of 1 to 4 carbon atoms or
aromatic such as C.sub.6 H.sub.5, C.sub.6 H.sub.4 CH.sub.3, naphthyl;
olefins such as trans-1,2-dichloroethylene; inorganic salts such as
cyanides, isocyanates, thiocyanates, thiocyanides, sulfides, hydrosulfides
and iodides wherein the metals are sodium or potassium; and hydrogen
sulfide as well as any mixtures thereof. A preferred second complexing
agent is a solution of acetic acid and pyridine in a weight ratio of from
about 7:1 to about 4:1 and most preferably of from about 6:1 to about 5:1.
Previously employed methods for catalyst removal have dealt with
coagulation of the polymer solution in dilute aqueous inorganic acid
and/or addition of polar organic solvents such as alcohols, ketones, or
hot water/steam. When this approach was tried in the first two embodiments
of the present invention, the product obtained still contained appreciable
quantities of catalyst, resulting in poor heat aging and poor oil
resistance of the compounded and cured elastomer derived from this
product. The use of dilute aqueous inorganic acids for the first and
second embodiments of the present invention resulted in a product with
embrittlement, and for the first embodiment only, partial loss of the
product in the aqueous acid solution.
EXAMPLE 11
First Embodiment
Under nitrogen, 100 grams of the product of Example 1 was dissolved in
several portions in one-half gallon of dry tetrahydrofuran in a one gallon
high pressure reactor equipped with a paddle stirrer. The copolymer was
completely dissolved in about four hours.
Preparation of the Hydrogenation Catalyst Solution
Under argon, a solution of 8.3 grams (12 weight percent) of cobalt (II)
neodecanoate in mineral spirits and 17.5 grams hexamethylphosphoric
triamide was prepared and cooled by means of an ice bath to about
3.degree. C. To this purple solution was added, drop-wise, 26.7 grams
triethylaluminum (25 weight percent, 1.9 molar solution) reductant in
toluene. Evolution of gases occurred and the purple solution turned brown
upon the addition of the triethylaluminum solution. After the addition of
the triethylaluminum, a hydrogenation catalyst solution was stirred under
nitrogen for one hour at room temperature.
The hydrogenation catalyst was then added slowly to the stirred copolymer
solution under nitrogen followed by the introduction of hydrogen (500
psi). Periodically, the reactor was repressurized to 500 psi in order to
compensate for hydrogen uptake by the polymer. When hydrogen uptake at
room temperature ceased, the polymer solution was heated to 50.degree. C.
and the hydrogen pressure increased to 1000 psi. Again, repressurization
was continued to compensate for hydrogen uptake by the polymer. After a
total time of about six hours, hydrogen uptake stopped. The polymer
solution was then cooled to room temperature. Excess hydrogen was vented
and replaced with a nitrogen blanket. A solution of glacial acetic acid
(200 grams) and pyridine (40 grams), deoxygenated by bubbling in nitrogen
was then added under nitrogen to the polymer solution. After stirring for
one hour at room temperature, the polymer solution was coagulated in hot
(70.degree. C.) water, filtered and dried in air (100.degree. C., four
hours), followed by drying in vacuum (80.degree. C., 1 mm Hg, two hours).
The action of acetic acid/pyridine solution on the cobalt ions under
anaerobic conditions was important in rendering the residual cobalt
catalyst (intimately mixed in with the polymer) innocuous to polymer
degradation. Without the acetic acid treatment, the hydrogenated polymer
exhibits poor heat aging and high oil swell in hydrocarbon oils. When
acetic acid/pyridine solution is added to the solution of the hydrogenated
polymer in the presence of air, prior to polymer coagulation, heat aging
is not improved.
The hydrogenated random copolymer of Example 11 is compounded and evaluated
in a side-by-side comparison with a nitrile rubber available from
Nippon-Zeon having 36 weight percent acrylonitrile. The control Example 12
and the invention Example 13 are both cured with sulfur. The evaluation is
set out in Table V. All values are parts by weight.
TABLE V
______________________________________
Example 12
Example 13
Control Present Invention
______________________________________
Stearic Acid 1 1
Zinc Oxide 5 5
Vanox ZMTI 2 2
Nangard 445 2 2
N550 Block 50 50
Spider Sulfur .2 .2
Methyl Tuads, TMTD
1.5 1.5
Ethyl Tuads, TETD
1.5 1.5
Santocure, CBTS 1.0 1.0
Zippon-Zeon 100.00
Nitrile Rubber
Product of Example 6 100.00
Rheometer (190.degree. C., 3.degree. Arc, 100 cpm, Micro Die)
ML (lbf. in) 10.0 5.1
MHF (lbf. in) 58.6 38.6
T.sub.s 2 (min.)
1.5 0.9
T'90 (min.) 2.7 1.7
Cure Time (min.)
4.0 4.0
Cure Time (min.)
6.0.sup.a 6.0.sup.a
Original Properties (Cured at 190.degree. C.)
Stress at 100% (psi)
383 383
Stress at 200% (psi)
732 759
Stress at 300% (psi)
1161 1234
Tensile Strength (psi)
2736 2939
Elongation, Ultimate (%)
850 788
Hardness, Shore A (pts)
71 70
Compression Set (ASTM D395, Method B, 70 hr, 150.degree. C.)
Set (%) 90.1 85.1
Gehman Low Temperature Torsion Test
Freeze Point (.degree.C.)
-26 -26
ASTM #3 Oil (170 hr. 150.degree. C.)
Volume Change (%)
19 19
Air Test Tube (70 hr. 175.degree. C.)
Tensile, Ultimate (psi)
2815 2792
Tensile Change (%)
3 -5
Elongation, Ultimate (%)
399 386
Elongation Change (%)
-53 -51
Hardness, Shore A (pts)
80 80
Hardness Change (pts)
+0 +10
______________________________________
.sup.a Tempered (4 hr, 177.degree. C.)
The hydrogenated random copolymer of Example 11 is compounded and evaluated
in a side-by-side comparison with a nitrile rubber available from
Nippon/Zeon having 36 weight percent acrylonitrile. The control Example 14
and the Invention Example 15 are both cured with peroxide. The evaluation
is set out in Table VI. All values are parts by weight.
TABLE VI
______________________________________
EXAMPLE EXAMPLE 15
14 PRESENT
CONTROL INVENTION
______________________________________
Structol WB-222 2.0 2.0
Stearic Acid 1.0 1.0
AgeRite Stalite S
2.0 2.0
N550 Block 40.0 80.0
Ricon 153D 4.0 4.0
Vulcup 40KE 10.0 10.0
Tetrono A 0.1 0.1
Product of Example 6
-- 100.0
Nippon-Zeon 100.00 --
Nitrile Rubber
Mooney Viscometer (125.degree. C., Large Rotor)
Minimum Viscosity
54.6 39.0
T.sub.5 (min) >35 >35
T.sub.35 (min) >35 >35
Rheometer (190.degree. C., 3.degree. C. Arc, 100 cpm, Micro Die)
ML (lbf. in) 12.7 4.9
MHF (lbf. in) 127.3 30.6
T.sub.s 2 (min.)
0.9 1.2
T'90 (min.) 3.5 4.0
Cure Time (min) 4.0 4.0
Cure Time (min) 6.0 6.0
(Compression Set Buttons)
Cure Time (min) 4.0 4.0
(Plied discs)
Original Properties (Cured at 190.degree. C.)
Stress at 100% (psi)
650 550
Stress at 300% (psi)
-- 3100
Tensile Strength (psi)
3680 3500
Elongation, Ultimate (%)
300 350
Hardness, Duro A (pts)
70 69
Gehman Low Temperature Torsion Test
Freeze pt. (.degree.C.)
-30.7 -30.7
ASTM #3 Oil (70 hr, 150.degree. C.)
Tensile, Ultimate (%)
31.25 3177
Tensile Change (%)
-15 -9
Elongation, Ultimate (%)
290 309
Elongation Change (%)
-3 -11
Hardness, Shore A (pts)
60 60
Hardness Change (pts)
-10 -9
Volume Change (%)
18 18
Air Test Tube (70 hr, 175.degree. C.)
Tensile, Ultimate (psi)
1756 1789
Tensile Change (%)
-52 -49
Elongation, Ultimate (%)
108 112
Elongation Change (%)
-64 -68
Hardness, Shore A (pts)
75 75
Hardness Change (pts)
5 6
______________________________________
EXAMPLE 15a
A sample of hydrogenated butadiene/2-vinylpyridine copolymer was made as in
Example 11, except using cobalt (II) octoate instead of cobalt (II)
neodecanoate as the transition metal catalyst component. Formula A.sub.u
represents the unhydrogenated starting material, and formula A.sub.h the
hydrogenated product.
##STR8##
The proton magnetic resonance spectrum of the unhydrogenated starting
material of Formula A.sub.u and the hydrogenated copolymer of Formula
A.sub.h above were recorded in FIGS. 1 and 2, respectively. The results
shown in FIG. 1 for the unhydrogenated butadiene/2-vinylpyridine copolymer
of Formula A.sub.u are set forth below in Table VIa.
TABLE VIa
______________________________________
Absorption (ppm)
Origin
______________________________________
0.75-3.00 Aliphatic protons
(i.e., hydrogen atoms
attached to saturated
carbon atoms)
1.75 Residual protons in
3.60 tetrahydrofuran -d.sub.8 used
as the PMR solvent
4.50-5.04 Protons H.sub.d from butadiene
copolymerized in a 1,2
fashion
5.04-5.80 Protons H.sub.a, H.sub.b from
butadiene copolymerized
in a 1,4 fashion and proton H.sub.c
from butadiene copolymerized
in a 1,2 fashion
6.45-8.70 Aromatic protons of the
pyridine ring
______________________________________
Calculation Of Mole Percent of Copolymerized 2-Vinylpyridine (formula
A.sub.u and FIG. 1)
Area represented by one H.sub.d proton=10.45/2=5.22.
Area represented by one H.sub.a proton=(area of H.sub.a, H.sub.b, H.sub.c
protons-area of H.sub.c proton)/2.
The area of the H.sub.c proton and one of the H.sub.d protons are equal.
Therefore, the area represented by one H.sub.a proton is
(63.86-5.22)/2=29.32.
Total area representing moles of butadiene in the copolymer is
29.32+5.22=34.54.
Total area representing moles of 2-vinylpyridine in the copolymer is
(14.28+15.16+27.57)/4=14.25.
Mole percent of 2-vinylpyridine copolymerized
##EQU1##
Check of Area in the Aliphatic Proton Region
Area expected=3.times. area of 1 H.sub.d +4.times. area of 1H.sub.a
+3.times. area of 1 aromatic
proton=3.times.5.22+4.times.29.32+3.times.14.25=175.69.
Area observed=218.99-(contribution from tetrahydrofuran)=218.99-25.8=193.19
(tetrahydrofuran makes equal contribution to the area at 1.75 and 3.60
ppm).
Thus, the above calculations show that the proton magnetic resonance
spectrum of FIG. 1 is accurate.
The proton magnetic resonance spectrum of the hydrogenated
butadiene/2-vinylpyridine copolymer of Formula A.sub.h is interpreted in
Table VIb below.
TABLE VIb
______________________________________
Absorption (ppm)
Origin
______________________________________
0.13-2.89 Aliphatic protons
(i.e., hydrogen atoms
attached to saturated
carbon atoms)
1.8 Residual tetrahydrofuran in
3.65 copolymer and residual protons
in tetrahydrofuran -d.sub.8 used as
the pmr solvent.
5.06-5.48 Protons H.sub.a, H.sub.b from residual
unsaturation
6.43-8.70 Aromatic protons of the
pyridine ring
______________________________________
It can be seen from FIG. 2, that olefinic protons H.sub.d, and hence
protons H.sub.c, are absent in the hydrogenated product (no absorption at
4.5-5.04 ppm observed in the starting material). Thus, the residual
unsaturation observed is due to the butadiene copolymerized in a 1,4
manner, that is, this trace absorption is assigned to the C--H olefinic
protons or hydrogen atoms attached to unsaturated carbon atoms of unit q
(formula A.sub.h).
CALCULATION OF MOLE PERCENT BUTADIENE UNHYDROGENATED
Area represented by moles of residual butadiene unit in
copolymer=2.49/2=1.24.
Aliphatic area contribution from residual butadiene unit=1.24.times.4=4.96.
Area represented by moles of 2-vinylpyridine copolymerized
(21.9+10.84+10.24);4=10.75.
Aliphatic area from copolymerized 2-vinylpyridine=3.times.10.75=32.25.
Aliphatic area observed=335.2-area due to
tetrahydrofuran=335.2-42.94=292.26.
Area due to saturated butadiene segments=292.26-32.25-4.96=255.05
Area representing the moles of saturated butadiene unit=255.05/8=31.88.
Mole percent unsaturation:
##EQU2##
Thus, the copolymer of Formula A.sub.h was hydrogenated to 97.8 percent by
weight.
______________________________________
Molecular weight
______________________________________
Butadiene unit 54
Saturated butadiene unit
56
2-Vinylpyridine unit
105
______________________________________
Mole percent of 2-vinylpyridine in the copolymer is
##EQU3##
which compares well with the 29.2 mole percent calculated for the starting
material. Hence, the pyridine ring has been unaffected by the
hydrogenation process. Thus, the polar character of the copolymer, and
hence the oil-resistance of the elastomer, is unaffected by the
hydrogenation process.
The infrared spectrum of the unhydrogenated butadiene/2-vinylpyridine
copolymer is compared with the hydrogenated butadiene/2-vinylpyridine
copolymer of Example 11 in FIGS. 3 and 4 respectively, and indicates for
the hydrogenated polymer the absence of absorptions at 970 and 915
cm.sup.-1 which ordinarily result from the olefinic carbon-hydrogen
out-of-plane bend (trans 1,4 copolymerized and 1,2 copolymerized
butadiene, respectively). Hence, the backbone and pendant unsaturation
have been completely or 100 percent saturated, and only the vinylpyridine
group of the hydrogenated copolymer remains unsaturated, which is
desirable. More particularly, the characteristic absorption (1590-1430
cm.sup.-1) due to the pyridine ring remains unaffected by the
hydrogenation process as shown in FIGS. 3 and 4. Thus, the polar character
of the copolymer, and hence the oil-resistance, is retained in the
hydrogenated copolymer.
The hydrogenated polymer of Example 11 was analyzed for cobalt by ashing
the sample, solubilization of the metals in the ashed sample with acid,
and measuring the metal concentration by atomic absorption. The cobalt
concentration was found to be 118 ppm.
When the procedure of Example 11 was repeated, and the hydrogenated
solution was worked up with glacial acetic acid only (150 ml) in the
absence of air, the cobalt concentration in the isolated copolymer was
reduced greatly by coagulating the polymer solution, with vigorous
stirring, in extremely dilute (0.45 wt percent) aqueous HCl. The catalyst
dissolved in the aqueous phase (cobalt 21 ppm and aluminum 35 ppm in the
isolated rubber). Thus, the use of glacial acetic acid alone, results in
more efficient removal of the cobalt catalyst. Using a more concentrated
aqueous solution (5 wt. percent aqueous HCl) resulted in dissolution of
part of the polymer and in the isolation of a cross-linked, brittle
product. Thus, desirably from about 0.1 to about 2.0 percent aqueous HCl
is used, preferably from about 0.25 to about 1.0 percent, and most
preferably about 0.45 percent. It is understood that inorganic acids other
than HCl, such as nitric acid or sulfuric acid at the same dilute weight
percent levels, could also be utilized with similar results.
EXAMPLE 16
Second Embodiment
Under nitrogen, 100 grams of the product of Example 6 was dissolved in
several portions in one-half gallon of dry tetrahydrofuran in a one-gallon
high pressure reactor equipped with a paddle stirrer. The copolymer was
completely dissolved in about four hours.
Preparation of the Hydrogenation Catalyst Solution
Under argon, a solution of 8.3 grams (12 weight percent) of cobalt (II)
neodecanoate in mineral spirits and 17.5 grams hexamethylphosphoric
triamide was prepared and cooled by means of an ice bath to about
3.degree. C. To this purple solution was added, drop-wise, 26.7 grams of
triethylaluminum (25 weight percent, 1.9 molar solution) reductant in
toluene. Evolution of gases occurred and the purple solution turned brown
upon the addition of the triethylaluminum catalyst. After the addition of
the triethylaluminum catalyst solution, a hydrogenation catalyst solution
was stirred under nitrogen for one hour at room temperature.
The hydrogenation catalyst was then added slowly to the stirred copolymer
solution under nitrogen followed by the introduction of hydrogen (500
psi). Periodically, the reactor was repressurized to 500 psi in order to
compensate for hydrogen uptake by the polymer. When hydrogen uptake at
room temperature ceased, the polymer solution was heated to 50.degree. C.
and the hydrogen pressure increased to 1000 psi. Again, repressurization
was continued to compensate for hydrogen uptake by the polymer. After a
total time of about six hours, hydrogen uptake stopped. The polymer
solution was then cooled to room temperature. Excess hydrogen was vented
and replaced with a nitrogen blanket. A solution of glacial acetic acid
(200 grams) and pyridine (37 grams) was deoxygenated with nitrogen and
then added to the polymer solution. After stirring for one hour at room
temperature, the polymer solution was coagulated in hot (70.degree. C.)
water, filtered and dried in air (100.degree. C., four hours), followed by
drying in vacuum (80.degree. C., 1 mm Hg, two hours).
The proton magnetic resonance spectrum of the hydrogenated butadiene methyl
acrylate copolymer is shown in FIG. 5. FIG. 5 indicates only a trace of
absorption in the olefinic proton region (5-6 ppm). Hence, the copolymer
is essentially 100 percent hydrogenated. The starting material can be
represented by formula B.sub.u and the hydrogenated material is
represented by formula B.sub.h.
##STR9##
FIG. 5 is interpreted below in Table VIc.
TABLE VIc
______________________________________
Absorption (ppm)
Origin
______________________________________
0.60-2.80 Aliphatic protons (i.e.,
hydrogen atoms attached
to saturated carbon atoms)
3.35-3.95
##STR10##
5.36 (trace) Residual unsaturation
7.26 From chloroform in chloroform-
-d pmr solvent
______________________________________
Calculation Of Mole Percent Copolymerized Methyl Acrylate
Area representing moles of methyl acrylate-10.00/3 or 3.33.
Aliphatic area resulting from copolymerized methyl
acrylate=3.times.3.33=10.00 (see Formula B.sub.u).
Therefore, the aliphatic area from hydrogenated butadiene
segments=(observed area)=10.00 or 76.61-10.00=66.61.
Hence, area representing moles of hydrogenated butadiene
segments=66.61/8=8.32
Mole percent of copolymerized methyl acrylate
##EQU4##
The molecular weight of copolymerized methyl acrylate is 86 and that of the
hydrogenated butadiene segments is 56.
The infrared spectrum of the starting material, see FIG. 6, when compared
with that of the hydrogenated copolymer, see FIG. 7, confirms the
conclusions reached by analysis of the proton magnetic resonance spectrum.
The bands at 970 and 915 cm.sup.-1 in the starting material are completely
absent in that of the product.
The absorption at 970 cm.sup.-1 originates from the olefinic
carbon-hydrogen out-of-plane bend due to the trans 1,4 copolymerized
butadiene unit, and that at 915 cm.sup.-1 from the carbon-hydrogen
out-of-plane bend due to the butadiene units copolymerized in a 1,2
fashion. The C.dbd.O stretching frequency of the ester carbonyl group
remains unchanged at 1740 cm.sup.-1 in the hydrogenated copolymer. Thus,
the polar character of the copolymer, and hence the copolymer
oil-resistance, is unaffected by the hydrogenation process.
EXAMPLE 17
Second Embodiment
This is a repeat of 16 except that the acetic acid-pyridine solution is
added to the hydrogenated polymer in the presence of air rather than under
anaerobic conditions.
The action of acetic acid and pyridine on the cobalt ions under anaerobic
conditions was important in rendering the residual cobalt catalyst
(intimately mixed in with the polymer) innocuous to polymer degradation.
Without the acetic acid-pyridine treatment, the hydrogenated polymer
exhibits poor heat aging and high oil swell in hydrocarbon oils. When
acetic acid-pyridine is added to the solution of the hydrogenated polymer
in the presence of air, prior to polymer coagulation, heat aging is not
improved.
The hydrogenated random copolymers of Examples 16 and 17 are compounded
with plasticizer, processing aids, amine anti-oxidant, curing agents and
sulfur donors. These examples are evaluated as Examples 18 and 19,
respectively in Table VII.
TABLE VII
__________________________________________________________________________
AGING: ENVIRONMENT: AIR OVEN; 70 HR., 175.degree.
Tensile,
Tensile,
Elongation
Elongation
Hardness
Hardness
psi change, %
% change, %
A, pts.
A, change, pts
__________________________________________________________________________
Example 18 2155 6 83 -55 90 11
(Compounded product
of Example 16,
anaerobic conditions)
Example 19 1930 -22 50 -72 89 11
(Compounded product
of Example 17, non-
anaerobic conditions)
__________________________________________________________________________
EXAMPLE 19a
A butadiene/2-methoxyethyl acrylate copolymer was synthesized as per
Example 6, starting with 40 parts of butadiene and 60 parts of
2-methyoxyethyl acrylate. The isolated rubber exhibited a glass transition
temperature of -60.degree. C. and a Mooney viscosity of 37
(ML[4,100.degree. C.]).
The polymer was hydrogenated and isolated as described in Example 16,
except for the use of cobalt (II) octoate as the transition metal
component for catalyst formation instead of cobalt (II) neodecanoate.
Formulas C.sub.u and C.sub.h represent the starting material and product,
respectively.
##STR11##
Analysis of the proton magnetic resonance spectrum of the starting material
(FIG. 8) and product (FIG. 9) is detailed below in Tables VIIa and VIIb,
respectively.
TABLE VIIa
______________________________________
Absorption (ppm)
Origin
______________________________________
0.66-2.60 Aliphatic protons (i.e.,
hydrogen atoms attached
to saturated carbon atoms)
2.95-3.40 OCH.sub.3 protons of ester group
3.40-3.76
##STR12##
3.90-4.38
##STR13##
4.70-5.06 Protons H.sub.d from butadiene
copolymerized in a 1,2 fashion
5.06-5.80 Protons H.sub.a, H.sub.b from butadiene
copolymerized in a 1,4 fashion
and proton H.sub.c from butadiene
copolymerized in a 1,2 manner
______________________________________
Calculation of the Mole Percent of Copolymerized 2- Methoxyethyl Acrylate
The absorption from 2.95-4.38 ppm, with a total area of 50.85
(36.28+14.57), represent the seven protons of the 2-methyoxyethyl group
##STR14##
Hence, the moles of copolymerized 2-methoxyethyl acrylate is represented by
an area of 50.85/7=7.26.
For the copolymerized butadiene segment, each H.sub.d proton is represented
by an area of 7.66/2 or 3.83.
Protons H.sub.a and H.sub.b are represented by (total area of H.sub.a,
H.sub.b, H.sub.c -area of H.sub.c [=area of H.sub.d ]) or
45.67-3.83=41.84. Therefore, one H.sub.a proton is represented by an area
of 41.84/2 or 20.92.
The moles of copolymerized butadiene is represented by 3.83+20.92=24.75.
Mole percent of copolymerized 2-methoxyethyl acrylate is
##EQU5##
which corresponds to
##EQU6##
Molecular weight of 2-methoxyethyl acrylate is 114, and that of butadiene
is 54.
Check of area in the aliphatic region. Expected area (Formula
C.sub.u)=(3.times. area representing copolymerized 2-methoxyethyl
acrylate)+(3.times. area representing 1 H.sub.d proton)+(4.times. area
representing 1 H.sub.a
proton)=(3.times.7.26)+(3.times.3.83)+(4.times.20.92)=117.
This compares well with the observed area of 121. Thus, the proton magnetic
resonance spectrum of FIG. 9 is accurate.
TABLE VIIb
______________________________________
Absorption (ppm)
Origin
______________________________________
0.6-2.74 Aliphatic protons
(i.e., hydrogen atoms
attached to saturated
carbon atoms)
3.10-3.47 OCH.sub.3 protons of ester
group
3.47-3.75
##STR15##
4.00-4.40
##STR16##
5.3-5.45 Olefinic CH protons due
to residual unsaturation from
butadiene copolymerized in a
1,4 manner
______________________________________
Calculation of the Mole Percent of Unhydrogenated Butadiene Segment in
Polymer
The absence of any signals in the 4.70-5.06 ppm region of FIG. 10 indicates
that unsaturation resulting from butadiene copolymerized in a 1,2 fashion
has been completely or 100 percent hydrogenated.
Residual moles of butadiene copolymerized in a 1,4 fashion is represented
by an area of 0.63/2 or 0.31.
The aliphatic contribution due to this residual unsaturation is represented
by an area of 0.31.times.4 or 1.24 (Formula C.sub.h).
Area representing moles of copolymerized 2-methoxyethyl acrylate is
##EQU7##
or 2.34.
Aliphatic contribution from the copolymerized 2-methoxyethyl acrylate is
represented by 2.34.times.3 or 7.02.
Therefore, the area representing the hydrogenated butadiene segments is
(area in the 0.6-2.74 ppm range)=(1.24+7.02) or 75.81-(1.24+7.02)=67.55.
Area representing the moles of hydrogenated butadiene is 67.55/8 or 8.44.
Mole percent unsaturation=
##EQU8##
Thus, the butadiene/methoxyethyl acrylate copolymer is hydrogenated to 97.8
percent by weight of the copolymer. The molecular weight of copolymerized
butadiene is 54, that of the hydrogenated butadiene segment 56, and that
of copolymerized 2-methoxyethyl acrylate 114.
The mole percent of 2-methoxyethyl acrylate is
##EQU9##
or 21.1 which compares well with the 22.7 percent calculated for the
starting copolymer. This confirms that the ester groups in the copolymer
are not hydrogenated. Thus, the polar character of the elastomer, and
hence elastomer oil-resistance, is retained in the hydrogenated product.
When the butadiene /2-methoxyethyl acrylate copolymer was hydrogenated as
detailed in Example 16, 100 percent hydrogenation of the backbone and
pendant unsaturation derived from butadiene was accomplished. The infrared
spectrum of the starting material (FIG. 10) when compared with that of the
hydrogenated product (FIG. 11), indicated the complete absence of the
absorption at 970 cm.sup.-1 due to the olefinic or unsaturated
carbon-hydrogen out-of-plane bend of the trans 1,4 copolymerized butadiene
unit and that at 915 cm.sup.-1 due to the olefinic or unsaturated
carbon-hydrogen out-of-plane bend resulting from butadiene copolymerized
in a 1,2 manner. The pendant ester groups were not affected as the C.dbd.O
stretching absorption at 1735 cm.sup.-1 is retained in the hydrogenated
product. Therefore, the polar character of the copolymer, and hence the
oil-resistance, is retained in the hydrogenated copolymer.
Also, the hydrogenation catalyst formed from cobalt neodecanoate is more
efficient than that formed from cobalt octoate as the transition metal
component. This is related to the higher water content in the commercially
available cobalt octoate solution (1.1 wt percent) than in cobalt
neodecanoate (0.32 wt. percent).
In a third embodiment of the present invention, fluorine containing
1,3-dienes are copolymerized with hydrocarbon 1,3-dienes. Glass transition
temperature and oil resistance are dependent upon the fluorine content.
More specifically, the polar groups in the copolymer contribute to polymer
oil-resistance while maintaining polymer thermooxidative stability.
Generally, the unsaturation of copolymerized fluorinated 1,3-dienes is
unaffected by the hydrogenation process. Thermooxidative stability is
improved greatly by removal of carbon/carbon unsaturation derived from the
hydrocarbon diene in the polymer, through hydrogenation. Thus,
thermooxidatively stable oil-resistant polymers with good low temperature
properties are obtained. The use of 1,3-butadiene as a comonomer yields
strong elastomers due to stretch crystallizable polyethylene segments in
the polymer that are formed by the hydrogenation process. The use of the
relatively inexpensive hydrocarbon-based dienes help lower raw material
costs.
A hydrogenated copolymer is prepared from at least two monomers. A
copolymer is formed by emulsion polymerization and then hydrogenated to
obtain a thermooxidatively stable composition. The copolymer is prepared
from two monomer classes. The first monomer comprises a fluorodiene of the
structure
##STR17##
wherein substituent a is independently hydrogen or fluorine, R.sub.15 is
hydrogen or a fluoro alkyl group containing from 1 to about 4 carbon atoms
and containing at least three fluoro atoms, with the proviso that both
R.sub.15 groups are not hydrogen, R.sub.16 and R.sub.17 are independently
fluorine, hydrogen or a fluoro alkyl group containing from 1 to about 4
carbon atoms and containing at least three fluorine atoms.
The second monomer is (a) a hydrocarbon diene comprising a straight chain
conjugated diene, a branched conjugated diene or mixtures thereof
containing from 4 to about 8 carbon atoms, or a monomer (b), (b) being a
monomer of the general formula CH.sub.2 .dbd.CR.sub.18 X wherein R.sub.18
is hydrogen or an alkyl group containing from 1 to about 4 carbon atoms,
and X is 2-pyridyl, 4-pyridyl, --COOR.sub.19, --CONR.sub.20 R.sub.21 or
--COOR.sub.22 OR.sub.19 wherein R.sub.19 is an alkyl group containing from
1 to about 4 carbon atoms, --CH.sub.2 CF.sub.3 or--CH.sub.2 CF.sub.2
CF.sub.2 H, R.sub.20 and R.sub.21 are alkyl groups containing from 1 to
about 4 carbon atoms, and R.sub.22 is an alkylene group containing from 1
to about 4 carbon atoms. The second monomer may also comprise a mixture of
monomers (a) and (b). The mole ratio of diene (a): CH.sub.2 .dbd.CR.sub.18
X (b), when (b) is present, is from 1:7 to about 7:1 and wherein the mole
ratio of first monomer:second monomer is from about 4:3 to about 2:3.
The first monomer is a fluorodiene. Some representative examples of
fluorodienes of the above structures III through VII are:
##STR18##
The term "fluoroalkyl" as used herein signifies that hydrogens of an alkyl
group are replaced with fluorine. Structural examples of fluoro alkyl
groups are: --CF.sub.3, --CH.sub.2 CF.sub.3, --CHFCHF.sub.2, --CF.sub.2
CH.sub.2 F, --CHFCF.sub.3, --CF.sub.2 CHF.sub.2, --CF2CF.sub.3, --CH.sub.2
CH.sub.2 CF.sub.3, --CH.sub.2 CHFCHF.sub.2, --CH.sub.2 CF.sub.2 CF.sub.3,
--CH.sub.2 CH.sub.2 CH.sub.2 CF.sub.3, --CH.sub.2 CH.sub.2 CHFCHF.sub.2,
--CH.sub.2 CH.sub.2 CHFCF.sub.3, --CH.sub.2 CH.sub.2 CF.sub.2 CF.sub.3,
--CH.sub.2 CH.sub.2 CHFCHF.sub.2, --CH.sub.2 CH.sub.2 CHFCF.sub.3. This
list is intended to be merely illustrative and not exhaustive, and the
omission of a certain structure is not meant to require its exclusion.
Preferably the fluoro alkyl group contains from 1 to 2 carbon atoms and
has at least three fluoro atoms. Preferable fluoro alkyl groups are
--CF.sub.3, --CH.sub.2 CF.sub.3 , --CF.sub.2 CF.sub.3 or --CF.sub.2
CHF.sub.2. The most preferable fluoro alkyl group is --CF.sub.3.
One of the structural formulae III through VII is utilized as the first
monomer and its disclosure above is hereby incorporated in toto. The
second monomer is (a) a straight chain conjugated diene, a branched
conjugated diene, or mixtures thereof containing from 4 to 8 carbon atoms.
Examples of straight chain dienes are 1,3-butadiene, 1,3-pentadiene,
1,3-hexadiene, 1,4-hexadiene, 1,3-heptadiene, 2,4-heptadiene,
1,3-octadiene, 2,4-octadiene, and 3,5-octadiene. Some representative
examples of branched chain dienes are isoprene,
2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-hexadiene, 3methyl-1,3-hexadiene,
2-methyl-2,4-hexadiene, 3-methyl-2,4-hexadiene,
2,3-dimethyl-1,3-pentadiene, 2,4-dimethyl-1,3-pentadiene,
2-ethyl-1,3-pentadiene, and 3-ethyl-1,3-pentadiene. The preferred dienes
for the practice of the invention are butadiene and isoprene.
The second monomer may also be (b), a monomer of the general formula
CH.sub.2 .dbd.CR.sub.18 X wherein R.sub.18 is hydrogen or an alkyl group
containing from 1 to about 4 carbon atoms, and X is 2-pyridyl, 4-pyridyl,
--COOR.sub.19, --CONR.sub.20 R.sub.21 or --COOR.sub.22 OR.sub.19 wherein
R.sub.19 is an alkyl group containing from 1 to about 4 carbon atoms,
--CH.sub.2 CF.sub.3 or --CH.sub.2 CF.sub.2 CF.sub.2 H, R.sub.20 and
R.sub.21 are alkyl groups containing from 1 to about 4 carbon atoms, and
R.sub.22 is an alkylene group containing from 1 to about 4 carbon atoms;
or mixtures of diene (a) and CH.sub.2 .dbd.CR.sub.18 X (b), wherein the
mole ratio of diene (a): CH.sub.2 .dbd.CR.sub.18 X (b), when (b) is
present, is from 1:7 to about 7:1 and wherein the mole ratio of first
monomer:second monomer is from about 4:3 to about 2:3.
Preferably R.sub.18 is hydrogen or an alkyl group containing from 1 to 2
carbon atoms and most preferably R.sub.18 is hydrogen or methyl. When X is
--COOR.sub.19, R.sub.19 preferably is an alkyl group containing from to 2
carbon atoms, most preferably R.sub.19 is methyl. When X is --CONR.sub.20
R.sub.21, preferably R.sub.20 and R.sub.21 are alkyl groups independently
containing from 1 to 2 carbon atoms and most preferably R.sub.20 and
R.sub.21 are methyl. When X is --COOR.sub.22 OR.sub.19, preferably
R.sub.22 is an alkylene group containing from 1 to about 2 carbon atoms
and R.sub.19 is an alkyl group containing from 1 to about 2 carbon atoms.
When R.sub.18 is hydrogen or methyl and X is --COOR.sub.19, some examples
of CH.sub.2 .dbd.CR.sub.18 X are acrylates, methacrylates, fluorinated
acrylates, or fluorinated methacrylates When R.sub.18 is hydrogen or
methyl and X is --CONR.sub. 20 R.sub.21, CH.sub.2 .dbd.CR.sub.18 X may be
tertiary acrylamides or tertiary methacrylamides. When R.sub.18 is
hydrogen or methyl and X is --COOR.sub.22 OR.sub.19, some examples of
CH.sub.2 .dbd.CR.sub.18 X are alkoxyalkyl acrylates or methacrylates.
When the second monomer comprises both (a) and (b), the mole ratio of diene
(a): CH.sub.2 .dbd.CR.sub.18 X(b) is from about 1:7 to about 7:1,
preferably 1:5 to about 5:1 and most preferably 3:1 to about 4:1.
The hydrogenated copolymers of the third embodiment of the present
invention also have utility as high temperature oil-resistant elastomers.
The hydrogenated copolymers of this third embodiment may be solids or
liquids, depending on molecular weight. These hydrogenated copolymers
serve as thermooxidatively stable oil-resistant elastomers or as impact
modifiers for plastics. Products made from these elastomers find use for
seals, gaskets, and hoses. The liquid polymers can be used as processing
aids and/or modifiers in rubber and plastic compounding.
The first step in the preparation of an oil-resistant elastomer is in
forming a copolymer. The copolymer is formed by emulsion polymerization.
For the formation of the copolymer, the mole ratio of the first
monomer:second monomer is from about 4:3, preferably 2:3, and most
preferably 1:1.
The copolymer is made in a conventional manner. That is, the above-noted
monomers are added to suitable amounts of water in a polymerization vessel
along with one or more conventional ingredients and polymerized. The
amount of polymerized solids or particles is generally from about 15
percent to about 50 percent with from about 25 to about 35 percent by
weight being desired. The temperature of polymerization is generally from
about 5.degree. C. to about 80.degree. C. with from about 5.degree. C. to
about 20.degree. C. being preferred. Typically in excess of 60 percent
conversion is obtained with from about 80 percent to about 85 percent
conversion being preferred. The copolymerization is generally initiated by
free radical catalysts which are utilized in conventional amounts, with
examples of such catalysts being those discussed above with regard to the
first two embodiments of the present invention, which discussion is hereby
fully incorporated by reference.
Inasmuch as the copolymers are prepared via an emulsion latex
polymerization route, anionic emulsifying aids are utilized. Thus, various
conventional anionic surfactants and anionic electrolytes known to the art
as well as to the literature are utilized, with the discussion thereof
with respect to the first two embodiments of the invention being hereby
fully incorporated by reference.
Molecular weight modifiers are also utilized to maintain the molecular
weight within desirable limits as otherwise the viscosity of the polymer
would be exceedingly high for subsequent handling, processing, and the
like. Generally, known conventional molecular weight modifiers can be
utilized such as are discussed above with respect to the first two
embodiments of the present invention, which discussion is hereby fully
incorporated by reference.
Yet another conventional emulsion latex additive is various short stop
agents which are added generally to stop the polymerization and to tie up
and react with residual catalysts. Such agents are discussed above with
respect to the first two embodiments of the invention and such discussion
is hereby fully incorporated by reference.
A cationic coagulant polymer also is utilized in the third embodiment of
the invention to coagulate the anionic emulsifying aids such as the
various anionic surfactants and the various anionic electrolytes utilized,
and the discussion thereof with respect to the first two embodiments of
the present invention is hereby fully incorporated by reference.
The cationic polymeric coagulant treated copolymer latex of the third
embodiment of the invention generally results in a slurry of rubber crumbs
in a clear aqueous liquid. The crumbs contain the various anionic
emulsifying aids physically incorporated therein. Such crumbs can be
separated in any conventional manner as by filtering. Inasmuch as the
anionic emulsifying aids have been rendered innocuous, multiple washing
steps or other expensive, tedious process steps such as solvent extraction
are not utilized.
The copolymer of the third embodiment of the present invention once dried
as by conventional means, has improved properties such as good water
resistance, good adhesion properties, non-interference with cure systems
when cured, reduce fouling of molds during the manufacture of parts,
improved electrical insulating properties, and the like. Such copolymers
can accordingly be utilized as adhesives, that is polymeric adhesives,
binders, films, e.g., electrical insulating films, coatings such as for
electrical circuit boards along with other conventional coating additives
and fillers known to the art and to the literature, and the like. Suitable
adhesive uses include metal-to-metal adhesion, metal-to-fabric adhesion,
metal-to-plastic adhesion, and the like. Additionally, the polymers of the
third embodiment of this invention have utility in the automotive area
such as in hoses, gaskets, seals, and timing belts.
The copolymer can be prepared with a mercaptan chain transfer agent
composition comprising (a) at least one mercaptan chain transfer agent and
optionally (b) at least one non-polymerizable material which is miscible
with the mercaptan chain transfer agent. Suitable mercaptans include those
discussed above with respect to the first two embodiments of the present
invention, which discussion is hereby fully incorporated by reference.
The chain transfer composition may comprise, in addition to the mercaptan,
at least one non-polymerizable material which is miscible with the
mercaptan and is substantially insoluble in water, and the discussion
thereof with regard to the first two embodiments of the present invention
also is hereby fully incorporated by reference.
The molecular weight of the copolymers of the third embodiment of the
present invention have a weight average molecular weight of from about
20,000 to about 1,000,000; desirably from about 200,000 to about 750,000;
and preferably from about 400,000 to about 500,000.
The third embodiment of the present invention will be better understood by
reference to the following examples.
Example 20 below outlines the emulsion polymerization of
1,1,2-trifluorobutadiene and butadiene.
EXAMPLE 20
Third Embodiment
To a 1 liter beverage bottle was added 121 g water. The water was
deoxygenated by bubbling in nitrogen before mixing in any additional
components. Added were 2.0 g 45 percent sodium lauryl sulfate emulsifier,
0.063 g sodium naphthalene sulfonate secondary emulsifier and 0.075 g
sodium carbonate electrolyte. A magnetic stirrer bar was added to the
bottle which was flushed with nitrogen and fitted with a septum. About
21.2 g 1,1,2-trifluoro-1,3-butadiene was generated per a procedure of J.
Org. Chem., 53, 2304 (1988) and condensed directly into the cooled (dry
ice/acetone) beverage bottle. About 10 g liquid butadiene was then
injected into the bottle via syringe, and then 0.26 g t-dodecylmercaptan
chain transfer agent was also injected and the contents were gradually
allowed to warm up to 5.degree. C. in an ice bath.
The following were freshly dissolved in 10 ml of deoxygenated water: About
0.0124 g sodium hydrosulfite oxygen scavenger, 0.0037 g trisodium ethylene
diamine tetraacetate trihydrate complexing agent for iron ions, 0.0056 g
sodium ferric ethylenediamine tetraacetate and 0.0391 g sodium
formaldehyde sulfoxylate. One-half of this solution was injected into the
beverage bottle followed by the introduction of 0.062 g paramenthane
hydroperoxide initiator. After stirring for 4 hours at 5.degree. C., the
contents were allowed to gradually warm up to room temperature overnight.
After the bottle was vented 0.1 g hydroxyl ammonium sulfate short stop
dissolved in 1 ml water was added to the latex and stirring was continued
for 15 minutes before adding 1.2 g 40 percent Aquamix 115 antioxidant.
Stirring was continued for 20 more minutes and the latex was coagulated in
70.degree. C. water containing 1.5 weight percent of aluminum sulfate. The
rubbery crumbs (90 percent yield) were washed with water and dried in air
(70.degree. C.), followed by vacuum drying at 60.degree. C. and 1 mm Hg
for 4 hours.
The cis and trans microstructures from the hydrocarbon diene generally are
hydrogenated to linear polyethylene segments which are responsible for the
improved mechanical properties of the elastomer due to stretch
crystallinity (A. H. Weinstein, Rubber Chemical Technology 57, 203
(1984)).
The copolymer once obtained in the third embodiment of the invention as
described above is then subjected to hydrogenation in the presence of a
transition metal catalyst, trialkylaluminum, and a complexing the absence
of BF.sub.3 or BF.sub.3 etherate.
Either a homogeneous or a heterogeneous catalyst may be used for the
hydrogenation although a homogeneous catalyst is preferred. Since a
homogeneous catalyst dissolves in solution, good contact is obtained with
the high molecular weight random polymer or copolymer. The homogeneous
catalysts are transition metal catalysts of either iron, cobalt, or
nickel. These metals are present as halides, acetates, or
acetylacetonates. Other homogeneous catalysts that can be employed are
palladium, platinum or rhodium present as tetrakistriphenylphosphine
palladium (0), tetrakistriphenylphosphine platinum (0) or
tristriphenylphosphine rhodium chloride.
The transition metal catalyst is employed with trialkylaluminum compounds,
wherein the alkyl group contains from 1 to about 4 carbon atoms, which
functions as a reducing agent. Other reducing agents that can be employed
are dialkyl aluminum hydride, the dialkyl aluminum alkoxides of 1 to 4
carbon atoms, sodium borohydride, and lithium aluminum hydride.
Additionally, other reductants are alkyl lithium, dialkyl magnesium, and
alkyl magnesium halide wherein the alkyl groups are from 1 to 4 carbon
atoms, and the halide is chloride or bromide.
The mole ratio of transition metal catalyst: reducing agent is usually from
1:10, preferably 1:6, and most preferably from 1:4.
In accordance with one of the main features of the present invention, the
transition metal catalyst complexes with a complexing agent. Without a
complexing agent, addition of the catalyst to the polymer solution causes
gelation. This is due to the metal ion of the transition metal catalyst
complexing with the polar groups on the polymeric chains. A gelled polymer
is difficult to hydrogenate to a high degree. Also, a partially
crosslinked polymer results. These factors cause the elastomer to be
poorer in heat aging and physical properties when compared to the polymers
of this invention In the third embodiment of the present invention the
complexing agents complex with the catalyst in order to prevent the
catalyst from excessive bonding to the polar functionalities.
Thus, in accordance with one of the important features of the present
invention, unexpectedly high degrees of hydrogenation of the copolymer
unsaturated olefinic backbone have been achieved, which improves the heat
resistance of the copolymer. Such unexpectedly good results have been
achieved through the use of a complexing agent for the hydrogenation
catalyst which prevents "poisoning" of the catalyst by the polar groups of
the copolymer thereby enabling the catalyst to complex with unsaturated
sites along the olefinic copolymer backbone to achieve such high levels of
hydrogenation thereof. The degree of hydrogenation achieved in the third
embodiment of the present invention is greater than about 80 percent;
preferably greater than about 85 percent; and most preferably greater than
95 percent hydrogenation of the olefinic unsaturated backbone of the
produced copolymers.
The amount of complexing agent employed is related to the relatively low
catalyst level. Generally, the mole ratio of catalyst complexing agent is
from 1:10, preferably 1:8; and most preferably 1:6. The complexing agents
for the catalysts are hexamethylphosphoric triamide,
tetramethylethylenediamine, phosphines of the general formula
(R.sub.23).sub.3 P, phosphites of the general formula (R.sub.23).sub.3 P
wherein R.sub.23 is an alkyl group containing from 1 to about 6 carbon
atoms, a phenyl group or a substituted aromatic group wherein the
substituent is an alkyl group containing from 1 to 2 carbon atoms such as
o-tolyl.
Solvents for the hydrogenation are well known in the art. An exemplary list
of solvents are xylenes, toluenes, anisole, dioxane, tetrahydrofuran,
hydrocarbons such as hexanes, heptanes, and octanes and chlorinated
hydrocarbons such as chlorobenzene and tetrachloroethane, trisubstituted
amines such as triethylamine and tetramethylethylene diamine.
The temperature of hydrogenation is generally from about 25.degree. C. to
about 150.degree. C. with from about 25.degree. C. to about 50.degree. C.
being preferred.
Removal of the transition metal catalyst is difficult and expensive. This
is due to the high molecular weight of the polymer and also that the
catalyst is intimately associated with the polymer. A catalyst, when left
in contact with the hydrogenated polymer, shows a degradative action. This
action is discussed in a paper titled "Rule of Metals and Metal
Deactivators in Polymer Degradation," Z. Osawa, Polymer Degradation and
Stability, 20, 203 (1988). An approach of this invention was to remove the
catalyst from the polymer and also to render the residual catalyst
innocuous, that is, to deactivate the catalyst by the addition of a second
complexing agent after hydrogenation in the absence of air. If the
catalyst is not rendered innocuous, the polymer shows poor heat aging and
high oil swell. Some examples of the second complexing agents are weak
organic acids containing from 1 to about 4 carbon atoms such as formic
acid, acetic acid, and propionic acid; diacids containing from 2 to about
6 carbon atoms such as oxalic acid, malonic acid, succinic acid, glutaric
acid, and adipic acid; amino acids of to about 4 carbon atoms such as
glycine, alanine, alphaglutaric acid, betaglutaric acid, and gammaglutaric
acid; citric acid; pyridine or substituted pyridine wherein the
substituent contains 1 to 2 carbon atoms; pyridine carboxylic acids such
as nicotinic acid and the corresponding sodium or potassium salts; alkyl
or aromatic nitriles containing from 1 to 6 carbon atoms; substituted
ureas or thioureas such as N,N-dialkyldithiocarbamate metal salts of 1 to
4 carbon atoms wherein the metal is lithium, sodium, or potassium,
hexamethylphosphoric triamide; tetramethylethylenediamine; phosphines
P(R.sub.24).sub.3 and phosphites P(OR.sub.24).sub.3 wherein R.sub.24 is
aliphatic with 1 to 4 carbon atoms or aromatic such as C.sub.6 H.sub.5,
C.sub.6 H.sub.4 CH.sub.3, naphthyl; olefins such as
trans-1,2-dichloroethylene; inorganic salts such as iodides, cyanides,
isocyanates, thiocyanates, thiocyanides, sulfides, hydrosulfides wherein
the metals are sodium or potassium; and hydrogen sulfide as well as any
mixtures thereof. A preferred second complexing agent is a solution of
acetic acid and pyridine in a weight ratio of from about 7:1 to about 4:1
and most preferably of from about 6:1 to about 5:1.
Previously employed methods for catalyst removal have dealt with
coagulation of the polymer solution in dilute aqueous inorganic acid
and/or addition of polar organic solvents such as alcohols, ketones, or
hot water/steam. When this approach was tried in the present invention,
the product obtained still contained appreciable quantities of catalyst
resulting in poor heat aging and high oil swell. The use of dilute aqueous
inorganic acids for the present invention resulted in a product with
embrittlement.
EXAMPLE 21
Third Embodiment
Under nitrogen, 15 grams of the product of Example 20 was dissolved in
several portions in 300 ml dry tetrahydrofuran in a 500 ml three-necked
round bottom flask equipped with a magnetic stirring bar. The copolymer
was completely dissolved in about four hours.
Preparation of the Hydrogenation Catalyst Solution
Under nitrogen, a solution of 1.6 grams 12 weight percent) of cobalt (II)
neodecanote in mineral spirits and 3.5 grams hexamethylphosphoric triamide
was prepared and cooled by means of an ice bath to about 3.degree. C. To
this purple solution was added, drop-wise, 6.4 ml of triethylaluminum (25
weight percent, 1.9 molar solution) in toluene. Evolution of gases
occurred and the purple solution turned brown upon the addition of the
triethylaluminum. After the addition of the triethylaluminum solution, a
hydrogenation catalyst solution was stirred under nitrogen for 1.5 hours
at room temperature.
The hydrogenation catalyst was then added slowly to the stirred copolymer
solution. The copolymer solution was then transferred under nitrogen into
an 800 ml pressure vessel, followed by the introduction of hydrogen (500
psi). Periodically, the reactor was repressurized to 500 psi in order to
compensate for hydrogen uptake by the copolymer. When hydrogen uptake at
room temperature ceased, the copolymer solution was heated to 50.degree.
C. and the hydrogen pressure increased to 1000 psi. Again,
repressurization was continued to compensate for hydrogen uptake by the
copolymer. After a total time of about six hours, hydrogen uptake stopped.
The copolymer solution was then cooled to room temperature. Excess
hydrogen was vented and replaced with a nitrogen blanket. A solution of
glacial acetic acid (30 ml) and pyridine (1 ml), deoxygenated by bubbling
in nitrogen, was then added under nitrogen to the copolymer solution.
After shaking for one hour at room temperature, the copolymer solution was
coagulated in hot (70.degree. C.) water, filtered and dried in air
(100.degree. C., four hours), followed by drying in vacuum (80.degree. C.,
1 mm Hg, two hours).
The action of the acetic acid/pyridine solution on the cobalt ions under
anaerobic conditions was important in rendering the residual cobalt
catalyst (intimately mixed in with the polymer) innocuous to polymer
degradation. Without this treatment, the hydrogenated polymer exhibits
poor heat aging and high oil swell in hydrocarbon oils. When acetic
acid/pyridine solution is added to the solution of the hydrogenated
polymer in the presence of air, prior to polymer coagulation, heat aging
is not improved.
It is well known to the art and to the literature that polymers and
copolymers based solely on fluorine containing 1,3-carbodienes yield
heat-resistant polymers if the number of fluorine atoms attached directly
to the carbon backbone is greater than 1. Heat resistance may vary
depending upon the point of attachment of the fluorine atom to the carbon
backbone, but in general, the higher the fluorine content, the higher the
thermooxidative stability of the polymer. In addition, the presence of
polar --C--F bonds in these polymers makes them oil-resistant. However,
such polymers are normally resinous and, hence, are not suitable for low
temperature (e.g., -30.degree. C.) elastomer applications. This is the
case, for example, with the homopolymer of 1,1,2-trifluorobutadiene Such
resinous materials are used primarily in fiber and coating applications.
Thus, although there has been a long-felt commercial need for polymers
which are useful in low temperature (e.g., -30.degree. C.) elastomeric
applications, and which exhibit good thermooxidative stability or heat
resistance and oil resistance, the above-discussed polymers and copolymers
based solely on fluorine containing 1,3-carbodienes are of limited
usefulness in such applications due to their relatively stiff resinous
nature despite their good heat and oil-resistant properties. (See U.S.
Pat. Nos. 2,979,489 and 3,218,303; and Technical Report 68-56-CM,
particularly page 8 thereof, by Relyea, Smith and Johnson, February, 1968,
Clothing and Organic Materials Laboratory, U.S. Army Natick Laboratories,
Natick, Mass. 01760).
On the other hand, copolymers of fluorinated 1,3-dienes with hydrocarbon
1,3-dienes are suitable for low temperature (e.g., -30.degree. C.)
elastomeric applications. However, the heat resistance of these polymers
is relatively poor due to the presence of the hydrocarbon segments
containing carbon-carbon unsaturation sites, thus making these copolymers
unsuitable for use in the area of above-described, long-felt commercial
need. For example, the copolymer of 1,1,2-trifluorobutadiene and butadiene
displays good low temperature elastomeric properties and oil resistance,
but poor heat resistance. (See Technical Report 68-56-CM by Relyea, Smith
and Johnson referenced above).
It is also well known to the art and to the literature that
acrylonitrile/1,3-butadiene copolymers exhibit improved heat resistance or
thermooxidative stability when the carbon-carbon unsaturation sites of the
butadiene segments are saturated. (See European Patent Application No. 0
111 412).
It is further known to the art and to the literature that fluorinated
1,3-dienes copolymerize with hydrocarbon 1,3 dienes in a 1,4
configuration. Thus, a 1,1,2-trifluorobutadiene/butadiene copolymer such
as is utilized as a starting material in the present invention is best
represented as follows by general Formula D.sub.u :
##STR19##
However, a tetrahydrofuran solution containing a hydrogenation catalyst and
a 1,1,2-trifluorobutadiene/butadiene copolymer such as described above,
becomes viscous and cannot be hydrogenated due to the drawing together of
the --CF.dbd.CH-- units of two different polymer chains, that is, due to
crosslinking of the polymer chains which is mediated by the hydrogenation
catalyst contained in the solution. Although polybutadiene by itself does
not exhibit this effect because it is not polar enough to draw the
catalyst in the same manner that the trifluorobutadiene polymer does, such
crosslinking between the trifluorobutadiene segments of different polymer
chains effectively prevents hydrogenation of the unsaturation sites in the
butadiene segments of the polymer chains, which saturation is necessary
for producing a high temperature, oil-resistant elastomer of the type
which has been commercially sought after. Complete or even partial
saturation or hydrogenation of such copolymers is unknown to the art and
to the literature.
In accordance with the present invention, the addition of a first
complexing agent to the tetrahydrofuran solution containing the
1,1,2-trifluorobutadiene/butadiene copolymer and hydrogenation catalyst
prior to hydrogenation, complexes with the catalyst and prevents excessive
complexing with the --CF.dbd.CH-- units of the 1,1,2-trifluorobutadiene
segments of the copolymer, so that the above-described crosslinking
between different polymer chains does not occur and a low viscosity
solution containing the copolymer results. Thus, the complexed catalyst is
more mobile and can reach, together with hydrogen, the desired sites of
unsaturation in the butadiene segments of the copolymer, enabling
hydrogenation or saturation to take place to a high degree. The
commercially sought after, high-temperature, oil-resistant elastomer
composition of the present invention thus is produced.
It should be noted that the unsaturation present in the trifluorobutadiene
segments of the 1,1,2-trifluorobutadiene/butadiene copolymer is not
critical to the production of a high-temperature, oil-resistant elastomer
composition of the present invention. More specifically, such unsaturation
in the trifluorobutadiene segments is not detrimental to the overall
thermooxidative stability of the copolymer of the invention due to the
presence of the fluorine substituents in the 1,1,2-trifluorobutadiene
segments.
A 1,1,2-trifluorobutadiene/butadiene copolymer was synthesized in emulsion
with an equimolar ratio of the two monomeric components. Subsequent to
polymerization, a single Tg, rather than two Tg's, was observed at
-45.degree. C. which indicates that a true copolymer was produced. From
the proton magnetic resonance spectrum of the isolated polymer in
tetrahydrofuran-d.sub.8 as shown in attached FIG. 13, it appears that both
of the monomers were incorporated into the polymer in the same ratio. In
keeping with the expected predominance of polymerization in a 1,4 fashion
for both monomers, the representation of the polymer structure would be as
follows in general Formula D.sub.u '.
##STR20##
The ratio of aliphatic protons to vinyl protons expected is 6:3 or 2:1,
which is observed in the attached spectrum in FIG. 12. Stated another way,
the portion of the graph which is bracketed and extends from about 0.4 ppm
to about 3.4 ppm represents the aliphatic protons or hydrogen atoms (i.e.,
6 in number) which are attached to saturated carbons in the copolymer. The
portion of the graph of from about 4.4 ppm to about 6.3 ppm represents
vinyl protons or hydrogen atoms (i.e., 3 in number) attached to
unsaturated carbon atoms of the copolymer. The area underneath the
respective portions of the graph represented by the vertically oriented
numbers 401.46 and 205.08, is directly proportional to the number of
hydrogen atoms which are attached to saturated or unsaturated carbon
atoms, respectively, in the synthesized copolymer.
The hydrogenated copolymer of the present invention is a mixture of the
structures described as Formulas D.sub.h and D.sub.h, below:
##STR21##
The proton magnetic resonance spectrum of the hydrogenated copolymer of the
present invention, as shown in attached FIG. 13, exhibits a decrease in
the vinyl protons or hydrogen atoms attached to unsaturated carbon atoms
of the copolymer, and an increase in the aliphatic protons or hydrogen
atoms attached to saturated carbons of the copolymer. This fact is evident
by viewing the peaks of FIG. 13 and comparing the same to the peaks of
FIG. 12, and also by summing the vertically oriented numbers under the
graph peaks, which represent the area under the respective peaks and is
directly proportional to the number of hydrogen atoms attached to
saturated carbon atoms and unsaturated carbon atoms in the copolymer.
The ratio of aliphatic protons to vinyl protons in the structure of Formula
D.sub.h should be 10:1, which is an increase from the 6:3 ratio observed
in the unhydrogenated starting copolymer, and the structure of D.sub.h '
should be completely hydrogenated. The ratio of aliphatic to vinyl protons
observed in the hydrogenated copolymer of the present invention, which is
a mixture of structures D.sub.h and D.sub.h ' is 11.8:1, indicating, in
all probability, 100 percent hydrogenation of the unsaturation derived
from the butadiene segment of the copolymer and partial hydrogenation of
the unsaturation derived from the fluorinated diene segment of the
copolymer. Thus, the high temperature, oil-resistant elastomer of the
present invention is obtained as evidenced in FIG. 13. It should be noted
that the new absorption from 4.1 to 4.8 ppm in FIG. 13 is assigned to the
proton H.sub.f resulting from the partial hydrogenation of the
--CF.dbd.CH-- linkage in the trifluorobutadiene segment of the copolymer.
While in accordance with the Patent Statutes, the best mode and preferred
embodiment has been set forth, the scope of the invention is not limited
thereto, but rather by the scope of the attached claims.
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